CapableObjects

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2010-04-17T15:47:00.001+02:00

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MDL File importer

2010-04-11T20:47:00.001+02:00

This is the third and last post on the Rational rose file importer.

Having this Rational Rose model:

I can now get this Modlr model:

The code is in the demos folder: PluginRoseFileRead

More importantly I tested this on a model I worked on some years ago for the swedish parliament:

It took almost two minutes to import it.

Notice to round magnifier in the diagram overview – we added this to Modlr some weeks ago, looks cool.

Declarative ViewModels and Taborder

2010-03-27T14:40:00.001+01:00

A very good friend of mine, Lars Olofsson, complained about the tab-order between controls in the ViewModels. The project he is working on uses the ViewModels A LOT. And as the work of developing this system goes on, little changes to the ViewModels get applied and the Taborder gets messier and messier.

He suggested that the Taborder should be made visible to the eye so that anyone touching the viewmodel definition could see if it was ok or not. That was a brilliant idea – why have it not always been that way:

Rational Rose Modeler

2010-03-27T13:55:00.001+01:00

So I had set out for doing the RationalRose file-format reader for Modlr. As I discussed earlier I was intimidated by the non-xml-file-format, and discouraged by the details in the format.

So I first made some logic that turned it into XML, then I made a plugin to Modlr that could deduce a Model from XML… So there is no escaping this I guess – I need to actually read and interpret the data…

BTW If anyone wonders why I have not done this until now it was because I was skiing – first in Sälen, Sweden – brilliant weather, ok hills, then in BadGastain, Austria – ok weather , brilliant hills!

   1: RoseImport ri = new RoseImport();  // This reads the mdl and turns it into XML

   2: ri.OpenFile(textBoxFileName.Text, true);

   3: _es = EcoSpace;

   4: _createdobjects = new Dictionary<string, IEcoObject>();

5:

   6: InstansiateObjects(ri.XDocument);       // This should interpret the xml content and match it with the model I have

   7: foreach (XDocument xd in ri.CatFiles)   // RoseImport also find CAT file references and reads those too

   8: {

   9:     InstansiateObjects(xd);

  10: }

Since I am lazy, stressed and living in Sweden, the country with the highest taxes in the world, I really need to be efficient about this…

My model was deduced from the XML so I am pretty sure that the names in the XML will be the same in my model.

Using the meta information from eco I can go like this to instantiate the correct objects:

   1: IEcoObject existing = null;

   2: XElement keyelement = xe.Elements("key") as XElement;

   3: if (keyelement != null && keyelement.Value != null)

   4: {

   5:     string Key = keyelement.Value;

   6:     if (_createdobjects.ContainsKey(keyelement.Value))

   7:         existing = _createdobjects[keyelement.Value];

   8: }

   9: if (existing == null)

  10: {

  11:     IClass iclass = EcoServiceHelper.GetTypeSystemService(_es).TypeSystem.

  12:             GetClassifierByName("ro_" + xe.Name.LocalName) as IClass; // My model prefixed all rose classes with ro_

  13:     existing = EcoServiceHelper.GetObjectFactoryService(_es).CreateNewObject(iclass);

  14:     if (keyelement != null && keyelement.Value != null)

  15:     {

  16:         _createdobjects.Add(keyelement.Value, existing);

  17:     }

18:

  19: }

Ok , moving on to the attributes:

   1: foreach (XElement child in xe.Elements())

   2: {

   3:     if (!child.HasElements)

   4:     {

   5:         IElement elem = existing.AsIObject().Properties[child.Name.LocalName];

   6:         if (elem != null && !(elem is IObjectList))

   7:             elem.SetValue<string>(child.Value);

   8:     }

   9:     else

  10:     {

  11:         // load association

  12:     }

  13: }

If my model had better typed values, like double, int, etc I would need to work on the parsing, but I am fine with strings.

And the associations:

   1: // load association

   2: IElement elem = existing.AsIObject().Properties[child.Name.LocalName];

   3: if (elem is IObjectList)

   4: {

   5:     foreach (XElement associationobject in child.Elements())

   6:     {

   7:         IEcoObject associaionInstansiatedObject=InstansiateObjects(associationobject);

   8:         if (associaionInstansiatedObject.AsIObject().UmlClass.ConformsTo((elem as IObjectList).UmlClass))

   9:             (elem as IObjectList).Add(associaionInstansiatedObject);

  10:         else

  11:             System.Diagnostics.Debug.WriteLine(string.Format("Tried to add a {0} to a list of {1}, association was {2}", 
                        associaionInstansiatedObject.AsIObject().UmlClass.Name, 
                              (elem as IObjectList).UmlClass.Name, child.Name.LocalName));

  12:     }

  13: }

Note the last line where I check if the loaded data actually will be valid to add in this association… Since my model was deduced from XML it is probably lacking important abstractions (inheritance). And sure enough, running this on a mdl file gave me this output:

   1: Tried to add a ro_Class to a list of ro_Class_Category, association was logical_models

   2: Tried to add a ro_Class to a list of ro_Class_Category, association was logical_models

   3: Tried to add a ro_Class to a list of ro_Class_Category, association was logical_models

   4: Tried to add a ro_Class to a list of ro_Class_Category, association was logical_models

   5: Tried to add a ro_Class to a list of ro_Class_Category, association was logical_models

   6: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

   7: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

   8: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

   9: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  10: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  11: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  12: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  13: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  14: Tried to add a ro_Association to a list of ro_Class_Category, association was logical_models

  15: Tried to add a ro_ClassDiagram to a list of ro_UseCaseDiagram, association was logical_presentations

This leads me to believe that the association logical_models really should point to some abstraction rather than to the ro_Class_Category itself… Keep in mind that I know nothing about what all this mean yet, I am just as ignorant to stuff maintained by IBM as IBM is of me (wow that is a lot).

So I change the model by introducing a superclass called LogicalModel (made sense since the association was called that):

BTW: I moved around the attributes (removing them from the subclasses to the superclass) with the newly implemented copy-paste function of the Modlr-tree (Yippy!).

I found some more missing abstractions that I added. Finally the output list was empty. No more errors.

At this point I need to actually understand what it is I am doing – after all I am supposed to understand the content of the rose file in order to turn the artifacts within into modlr objects (defined by, what we call, extendedmodellayer).

No better way than to use the EcoSpaceDebugger and autoforms. Load my sample mdl again:

There is a ro_ClassDiagram that looks interesting:

…it has a multi link called Items that contain ro_ClassView and ro_AssociationView…

Looking closer in the ro_ClassView – I guessing that this is what ModelLayer calls PlacedClass:

…I wonder how if finds the ro_class… I am guessing it uses the quidu reference…

Using the ecospace debugger I wrote this ocl: ro_Class.allinstances->select(quid='"3BDC6B1A02D7"') and sure enough:

So I will amend the model to keep this knowledge in a derived association.

The Derivation expression is “ro_Class.allinstances->select(quid=self.quidu)->first”

Not only does the derived association help me when looking in autoforms and writing code; it also ensures that things stay optimized. A derived association is subscribed to by the eco-runtime, and the value is cached until it changes. And when it changes it is merely marked as out of date, so it is only updated if someone tries to read it again.

It is easy to imagine that I would write code and look up the ro_Class from the ro_ClassView.quidu whenever I needed it; but the derived association removes the need for repetitive, error prone, performance hurting, hard to find code and brings it up in the light, as a first class member of the ro_ClassView ready to serve whenever I need it – available in the model for everyone to see. How beautiful is that?

So I am not going to bore you with all the details – I will continue to work on this – the main purpose of this post was to explain how I use eco to move away from time consuming hand coding techniques, towards building and using tools to get the job done.

Get out of the middle ages – become model driven.

Strongly typed thank you!

2010-02-21T19:46:00.001+01:00

This weekend I set out for doing a Rational Rose file import plugin for Modlr. I wrote the code that successfully traversed the rather strange file format that they use. Rational Rose is a pre-xml product:

1:

   2: (object Petal

   3:     version        47

   4:     _written       "Rose 8.0.0303.1400"

   5:     charSet        0)

6:

   7: (object Design "Logical View"

   8:     is_unit        TRUE

   9:     is_loaded      TRUE

  10:     quid           "4B7FCC8D02EF"

  11:     defaults       (object defaults

  12:     rightMargin     0.250000

  13:     leftMargin     0.250000

  14:     topMargin      0.250000

  15:     bottomMargin     0.500000

  16:     pageOverlap     0.250000

  17:     clipIconLabels     TRUE

  18:     autoResize     TRUE

  19:     snapToGrid     TRUE

  20:     gridX          0

  21:     gridY          0

  22:     defaultFont     (object Font

  23:         size           12

  24:         face           "Arial"

  25:         bold           FALSE

  26:         italics        FALSE

  27:         underline      FALSE

  28:         strike         FALSE

  29:         color          0

  30:         default_color     TRUE)

  31:     showMessageNum     3

  32:     showClassOfObject     TRUE

  33:     notation       "Unified")

  34:     root_usecase_package     (object Class_Category "Use Case View"

  35:     quid           "4B7FCC8D02F1"

So when I had all that done I thought that it would an easy and quick task to wrap that information into a model designed in eco so that I could populate it with objects from the file. Once that was done I planned to write the code that transformed from that rose model to the eco modellayer model…

But I immediately got super tired when I realized that I had to create some 30-40 classes with a lot of attributes and relations all by hand in order to hold the rational rose data from the file…

It seemed silly that I would need to do stuff by hand at all. After all we are the tool making species! So I started to think that this is a common scenario – I have a description, or data adhering to a description, in one format, and I want to have that as a model so I can code towards it with strongly typed classes ( the older (and wiser?) I get, I get increasingly more allergic to scripting ).

So if this is a common problem that at least I come across from time to time maybe I should solve that first?

I asked myself what format the data I need to handle usually come in : XML.

So to avoid losing focus of my initial problem all together I used my Rational Rose File decoder logic and made it spit out the same information as XML:

   1: <?xml version="1.0" encoding="utf-8"?>

   2: <root>

   3:   <Petal>

   4:     <name></name>

   5:     <key></key>

   6:     <version>47</version>

   7:     <_written>"Rose 8.0.0303.1400"</_written>

   8:   </Petal>

   9:   <Design>

  10:     <name>Logical View</name>

  11:     <key></key>

  12:     <is_unit>TRUE</is_unit>

  13:     <is_loaded>TRUE</is_loaded>

  14:     <quid>"4B7FCC8D02EF"</quid>

  15:     <defaults>

  16:       <defaults>

  17:         <name></name>

  18:         <key></key>

  19:         <rightMargin>0.250000</rightMargin>

  20:         <leftMargin>0.250000</leftMargin>

  21:         <topMargin>0.250000</topMargin>

  22:         <bottomMargin>0.500000</bottomMargin>

  23:         <pageOverlap>0.250000</pageOverlap>

  24:         <clipIconLabels>TRUE</clipIconLabels>

  25:         <autoResize>TRUE</autoResize>

  26:         <snapToGrid>TRUE</snapToGrid>

  27:         <gridX>0</gridX>

  28:         <gridY>0</gridY>

  29:         <defaultFont>

  30:           <Font>

  31:             <name></name>

The general idea was to write a plugin that given this XML, or a similar XML, or preferably any XML, could derive a model for me, saving me from doing stuff manually.

I know that some of you are thinking “oh boy this guy is writing a plugin in order to write a plugin in order to convert a rose file?”, and yes you are correct. But one plugin will be very generic – taking almost any XML and turning it into a modlr model.

So nothing fancy:

   1: XDocument xd = XDocument.Load(file);

   2: foreach (XElement xe in xd.Root.Elements())

   3: {

   4:     Analyze(xe);

   5: }

And the magic of the plugin:

   1: private Eco.ModelLayer.Class Analyze(XElement xe)

   2: {

   3:     Eco.ModelLayer.Class c = EnsureClass(GetNameFromXE(xe));

   4:     foreach (XAttribute xa in xe.Attributes())

   5:     {

   6:         EnsureAttribute(c, xa.Name.ToString());

   7:     }

   8:     foreach (XElement subxe in xe.Elements())

   9:     {

10:

  11:         if (subxe.FirstNode is XText || subxe.FirstNode==null)

  12:         {

  13:             // treat as model attribute

  14:             EnsureAttribute(c, GetNameFromXE(subxe));

  15:         }

  16:         else

  17:         {

  18:             // treat as model association

  19:             /*

  20:                 We treat to types of linking:

  21:                  single link may look like this:

  22:                      obj1

  23:                         attr1

  24:                         link

  25:                             attr1

26:

  27:              *   multilink often looks like this:

  28:                      obj1

  29:                         attr1

  30:                         link

  31:                             obj2

  32:                                attr1

  33:              */

  34:             if (subxe.Elements().Count() > 0 && 
                                (subxe.Elements().First().FirstNode is XText || subxe.Elements().First().FirstNode == null))

  35:             {

  36:                 Eco.ModelLayer.Class targetclass = Analyze(subxe);

  37:                 AssociationEnd ae = EnsureAssociation(c, targetclass, GetNameFromXE(subxe));

  38:                 if (ae!=null)

  39:                     ae.Multiplicity = "0..1";

  40:             }

  41:             else

  42:             {

  43:                 List<Eco.ModelLayer.Class> classesfoundinrelation = new List<Eco.ModelLayer.Class>();

  44:                 foreach (XElement xeObjectInAssoc in subxe.Elements())

  45:                 {

  46:                     Eco.ModelLayer.Class targetclass = Analyze(xeObjectInAssoc);

  47:                     if (classesfoundinrelation.IndexOf(targetclass) == -1)

  48:                         classesfoundinrelation.Add(targetclass);

  49:                 }

50:

  51:                 if (classesfoundinrelation.Count > 0)

  52:                 {

  53:                     // if classesfoundinrelation.Count>1 the association is most likely 
                               pointing to a super class of the classes found, but we dont have enough info - pick first

  54:                     AssociationEnd ae = EnsureAssociation(c, classesfoundinrelation[0], GetNameFromXE(subxe));

  55:                     if (ae!=null)

  56:                         ae.Multiplicity = "0..*";

  57:                 }

  58:             }

  59:         }

  60:     }

  61:     return c;

  62: }

63:

The logic to actually create a Class, an Attribute or a Relation looks like this:

   1: private AssociationEnd EnsureAssociation(Eco.ModelLayer.Class cfrom, Eco.ModelLayer.Class cto, string xName)

   2: {

3:

   4:     if (_esp != null)

   5:     {

   6:         var res = (from x in cfrom.AssociationEnd where x.OtherEnd != null && x.OtherEnd.Name == xName select x);

   7:         if (res.Count() == 0)

   8:         {

   9:             AssociationEnd ae1=new AssociationEnd(_esp);

  10:             AssociationEnd ae2 = new AssociationEnd(_esp);

  11:             Association a = new Association(_esp);

  12:             a.AssociationEnd.Add(ae1);

  13:             a.AssociationEnd.Add(ae2);

  14:             a.Package_ = _package;

  15:             ae2.Name = xName;

  16:             ae2.IsNavigable = true;

  17:             cfrom.AssociationEnd.Add(ae1);

  18:             cto.AssociationEnd.Add(ae2);

  19:             return ae2;

  20:         }

  21:         return res.First().OtherEnd;

  22:     }

  23:     return null;

  24: }

25:

  26: private void EnsureAttribute(Eco.ModelLayer.Class c, string xName)

  27: {

  28:     if (_esp != null)

  29:     {

  30:         foreach (ModelElement me in c.AllFeatures)

  31:         {

  32:             if (me is Eco.ModelLayer.Attribute)

  33:             {

  34:                 if (xName == (me as Eco.ModelLayer.Attribute).Name)

  35:                 {

  36:                     return;

  37:                 }

  38:             }

  39:         }

  40:         // not found

41:

  42:         Eco.ModelLayer.Attribute a=new Eco.ModelLayer.Attribute(_esp);

  43:         a.Name = xName;

  44:         if (_stringDataType==null)

  45:             _stringDataType=(from x in _esp.GetEcoService<IExtentService>().AllInstances<Datatype>()
                         where x.Name.ToLower()=="string" select x).First<Datatype>();

  46:         a.Type = _stringDataType;

  47:         c.Feature.Add(a);

48:

  49:     }

  50: }

51:

  52: private Eco.ModelLayer.Class EnsureClass(string xName)

  53: {

  54:     if (_esp != null)

  55:     {

  56:         string completename = _prefix + xName;

  57:         var result = (from x in _esp.GetEcoService<IExtentService>().AllInstances<Eco.ModelLayer.Class>()

  58:                       where (x.Name == completename && x.OwningPackage == _package) select x).ToArray<Eco.ModelLayer.Class>();

  59:         if (result.Count() == 0)

  60:         {

  61:             Eco.ModelLayer.Class c = new Eco.ModelLayer.Class(_esp);

  62:             c.Name = completename;

  63:             c.Package_=_package;

  64:             return c;

  65:         }

  66:         else

  67:             return result[0];

  68:     }

  69:     return null;

  70: }

  71:     }

I tried the logic on several different xml files that I found in my temp folder and found some special cases. This lead me to the conclusion that I needed at least two different strategies: one where the xml element has a generic name and the real name is given in some attribute. One example of this is the EcoMdl file format:

   1: <?xml version="1.0" encoding="utf-8"?>

   2: <contents>

   3:   <object type="Diagram" href="ClassDiagram_Diagram1">

   4:     <doc><![CDATA[]]></doc>

   5:     <modlrdiagram>diagramimages/efcd3388-264f-469f-b6e2-5e0a1dc68839.jpg</modlrdiagram>

   6:     <attribute name="ColorOnNew">0</attribute>

   7:     <attribute name="Id">efcd3388-264f-469f-b6e2-5e0a1dc68839</attribute>

   8:     <attribute name="SnapGridSize">15</attribute>

   9:     <attribute name="PresentationName">Diagram1</attribute>

  10:     <attribute name="ShowMethodSignatures">False</attribute>

  11:     <attribute name="ShowAssociationNames">DimDefaults</attribute>

  12:     <attribute name="ShowVisibility">False</attribute>

  13:     <attribute name="SquareNewAssociations">False</attribute>

  14:     <attribute name="SquareNewGeneralizations">False</attribute>

  15:     <attribute name="ShowMethodReturnTypes">False</attribute>

  16:     <attribute name="Name">Diagram1</attribute>

  17:     <link name="PlacedClass">

  18:       <object type="PlacedClass" href="Class1">

  19:         <attribute name="RenderedWidth">200,8</attribute>

  20:         <attribute name="id">0aac4fb8-5dd6-4082-b16b-73c07565fc57</attribute>

  21:         <attribute name="Color">1692800256</attribute>

  22:         <attribute name="Size">1</attribute>

  23:         <attribute name="LastKnownName">Class1</attribute>

  24:         <attribute name="RenderedHeight">49,25</attribute>

But the more common scenario is the format where the xml elements have specific names. Like the pad format:

   1: <?xml version="1.0" encoding="UTF-8"?>

   2: <XML_DIZ_INFO>

   3:   <MASTER_PAD_VERSION_INFO>

   4:     <MASTER_PAD_VERSION>3.01</MASTER_PAD_VERSION>

   5:     <MASTER_PAD_EDITOR>PADManager 2.0.46</MASTER_PAD_EDITOR>

   6:     <MASTER_PAD_INFO>Portable Application Description, or PAD for short, is a data set that is used by shareware authors to disseminate information to anyone interested in their software products. To find out more go to http://www.asp-shareware.org/pad</MASTER_PAD_INFO>

   7:   </MASTER_PAD_VERSION_INFO>

   8:   <RoboSoft>

   9:     <Company_UIN>CMP-009701CA593</Company_UIN>

  10:     <Company_Description></Company_Description>

  11:     <Product_UIN>APP-009701FB886</Product_UIN>

  12:     <Publish_on_CD>FALSE</Publish_on_CD>

  13:     <Search_String></Search_String>

  14:     <Press_Release_Search_String></Press_Release_Search_String>

  15:     <NewsFeed_Search_String></NewsFeed_Search_String>

  16:     <Search_Engine_Search_String></Search_Engine_Search_String>

  17:     <Web_Directories_Search_String></Web_Directories_Search_String>

  18:     <Search_String_Unique></Search_String_Unique>

  19:     <Comments_For_Reviewer></Comments_For_Reviewer>

  20:     <Additional_Categories></Additional_Categories>

  21:     <Backlink></Backlink>

  22:   </RoboSoft>

  23:   <Company_Info>

  24:     <Company_Name>CapableObjects.com</Company_Name>

  25:     <Address_1>Box 1200</Address_1>

  26:     <Address_2>Huddinge</Address_2>

  27:     <City_Town>Stockholm</City_Town>

I added a window that pops up when executing the plugin, it lets you pick the xml file, choose strategy, choose target package and GO:

And it gave me this (I dragged them onto the diagram myself)

Puh, now when I have a good starting point for the rational rose object model I can back to my original task… But that will be some other day…

(the plugin is in the demos folder for the next available eco build and it is called PluginXmlToModel)

Modlr plugins

2010-02-17T16:27:00.001+01:00

We added a plugin interface for Gaffr and ECO. We want to enable you to extend Modlr so that you can implement a special file format import, or export, or what have you.

This is how it works:

Given these two interfaces…

   1: namespace Modlr.Plugins

   2: {

   3:     public interface IModlrPlugin

   4:     {

   5:         string GetName();

   6:         List<IModlrPluginMenuOperation> ProvideOperations();

   7:     }

8:

   9:     public interface IModlrPluginMenuOperation

  10:     {

  11:         string GetName();

  12:         void CheckEnableOrExecute(IEcoServiceProvider esp, bool execute, 
                        IEcoObject maincontext, IEcoObject subcontext,out bool enabled );

  13:     }

  14: }

…you can implement a plugin in an assembly like this:

   1: public class Class1 : IModlrPlugin

   2: {

   3:     #region IModlrPlugin Members

4:

   5:     public string GetName()

   6:     {

   7:         return "Demo plugin";

   8:     }

9:

10:

  11:     public List<IModlrPluginMenuOperation> ProvideOperations()

  12:     {

  13:         List<IModlrPluginMenuOperation> ops = new List<IModlrPluginMenuOperation>();

  14:         ops.Add(new OperationShowDialog());

  15:         ops.Add(new OperationActOnClass());

16:

  17:         return ops;

  18:     }

19:

  20:     #endregion

  21: }

22:

The code above installs two Operations; OperationShowDialog and OperationActOnClass.

Looking closer on the operation ActOnClass:

   1: public class OperationActOnClass : IModlrPluginMenuOperation

   2: {

   3:     #region IModlrPluginMenuAction Members

4:

   5:     public void CheckEnableOrExecute(IEcoServiceProvider esp,
                      bool execute, Eco.ObjectRepresentation.IEcoObject maincontext, 
                      Eco.ObjectRepresentation.IEcoObject subcontext, out bool enabled)

   6:     {

   7:         enabled = false;

   8:         if (maincontext != null && maincontext.AsIObject().AsObject is Eco.ModelLayer.Class)

   9:         {

  10:             enabled = true;

  11:             if (execute)

  12:             {

  13:                 (maincontext.AsIObject().AsObject as Eco.ModelLayer.Class).Name += "X";

  14:             }

  15:         }

  16:     }

17:

  18:     public string GetName()

  19:     {

  20:         return "Operation on class";

  21:     }

22:

  23:     #endregion

  24: }

The code checks that the context is a class, and if it is the code says that the operation should be enabled. If this was an “execute” call we perform the desired logic – in this case I just add an “X” to the back of the class name.

You can do a lot of stuff in a plugin. You get access to the IEcoServerProvider for the EcoModelLayer. The Modlr application is a standard ECO-built-application so you can use the IOCLService to get to any object, of any class that builds up your model content. You can access Diagrams, PlacedClasses, StateMachines etc. You can inspect and set TaggedValues, you can run thru every Attribute and check for spelling errors. You can create reports that you share with other ECO/Gaffr users…

So even if the interface is very small and simple, it is very powerful.

When you build your Plugin you will want to reference the following assemblies (found in the eco or gaffr install directory):

Compile your plugin and put the assembly in the folder %ProgramData%/CapableObjects/Plugins

Restart Gaffr.net or VisualStudio and you will find your plugin operations in the context menu:

Simple and powerful.

ViewModels in ASP.NET

2010-02-14T21:07:00.001+01:00

I got a couple of questions about ViewModels in ASP.NET; and my conscience has stirred me to action. I was aiming to finish the immensely cool project that we call GaffrServer and I want to use the ASP.NET viewmodels to make that happen.

Side note on what GaffrServer is: Imagine that you prototype in Gaffr.net using the upcoming Application WPF framework WECPOF (oh I just love inventing code names for our projects: WECPOF - ECO + WPF – get it?), and you want persistence. You can write to a XML file, or set up a database… But you will also be able to connect to GaffrServer – GaffrServer is cloud service that you upload your model to, then you get back an url that is the up and running server side persistence mapper with the synchronization service running – WOW! I WANT IT NOW.

Anyway the GaffrServer project is sort of dragging its feet so I am better of just showing ASP.NET ViewModels.

I wrapped up a sample that looks like this:

Notice the derived attributes on OrderItem and Order:

   1: CostForRow = (self.Quantity*self.Article.Cost)+(self.Quantity*self.Article.Weight*self.Order.DeliveryType.CostPerKiloGram)

2:

   3: TotalCost = self.OrderItem->Collect(a|a.CostForRow)->sum()

(Note that the TotalCost actually use the derivation in CostForRow – super cool imho)

Then I did a ViewModel:

I know some of you might initially frown at the complexity, but trust me, you just click away and use the suggested columns that are available on the context menu – I seldom have a specific plan when I start – I think and do at the same time. That is the hallmark of a tool that is helping you…

The basic idea was to fill in an order, add OrderLines, set the correct Article on the OrderLine, see the price per row, and the total price, taking into account what delivery type you use…

There you go, a neat little list of requirements so easily said – and easily implemented.

I created a ECO ASP.NET application from the ECO Solution Wizard, Added the scriptmanager and an UpdatePanel to get Ajax behavior.

Then I add the ViewModelASPNET component, hook it up to the EcoSpaceManager, and tell it to use ViewModel ViewModelOrder:

I need to write some code to get test data and to hook up the ViewModelASPNET control to an order:

   1: private void Page_Load(object sender, System.EventArgs e)

   2: {

3:

   4:     if (!Page.IsPostBack)

   5:     {

   6:         Order order;

   7:         if (EcoSpace.GetEcoService<IExtentService>().AllInstances<Order>().Count == 0)

   8:         {

   9:             order = InitSomeTestData();

  10:         }

  11:         else

  12:             order = EcoSpace.GetEcoService<IExtentService>().AllInstances<Order>()[0];

  13:         ViewModelASPNET1.SetObject(order);

  14:     }

  15: }

16:

  17: private Order InitSomeTestData()

  18: {

  19:     Order order=new Order(EcoSpace);

  20:     order.CustomerName = "SomeName";

  21:     order.CustomerAddress = "SomeAddress";

  22:     order.DeliveryType = new DeliveryType(EcoSpace) { Name = "UPS", CostPerKiloGram = 20.5 };

  23:     new DeliveryType(EcoSpace) { Name = "Schenker", CostPerKiloGram = 19.5 };

  24:     new DeliveryType(EcoSpace) { Name = "DHL", CostPerKiloGram = 29.5 };

25:

  26:     new Article(EcoSpace) { Name = "Knife", Cost=127.5, Weight=0.25 };

  27:     new Article(EcoSpace) { Name = "Vobbler", Cost = 17.1, Weight = 0.15 };

  28:     new Article(EcoSpace) { Name = "Fishing rod", Cost = 527.5, Weight = 1.05 };

29:

  30:     EcoSpace.UpdateDatabase();

  31:     return order;

32:

  33: }

I also must init the viewmodels before they are used:

   1: protected void ScriptManager1_Init(object sender, EventArgs e)

   2: {

   3:     ViewDefinitionsInApplication.Init(EcoSpace);

4:

   5: }

Then I get something that looks like this:

Notice the crazy style on CostForRow, the style on TotalCost and on Selected orderitem – I get these by providing a css stylesheet that has styles using the names I set in the ViewModelColumns StyleRef property…

As you change deliverytype or anything else the TotalCost will be updated on the next postback.

In this demo I chose to use the setting ViewModelASPNET.PostbackOnComboboxChange="true"
I also chose to use the setting ViewModelASPNET.GridSizeFixedWithScrollbar="True"

The bits to run this is in the eco build after this date, it is in the demos called EcoASPNETWithViewModel

Using Blend with ECO

2010-01-17T15:18:00.001+01:00

Blend is the XAML-high-level tool. It is very powerful if you know what you are doing. Having that special designer eye that helps you to stop messing with something when it is done is probably a very useful skill when working with Blend – I do not have it, yet. But still here is my 5 minutes crash course into Microsoft Blend for ECO developers.

First: Blend is all about UI. Nothing about data. You can bind the UI to a datasource, but you cannot do anything else useful with the datasource in Blend – just use it.

Second: XAML is all about binding – in that sense it is very declarative. You do not do any imperative coding in Blend (ideally). Instead you declare rules that makes things happen for you; i.e. you declare bindings and animations.

I continued on the WPF-Hockey sample I wrote about earlier. To do anything cool in Blend you need to have an idea on what you want (that statement is sort of generic) – if that idea includes data then ECO is your best friend.

I find it useful to declare the processes in ECO, it helps me to keep my objectives clear and focused:

The SetUpGame thing I did in the previous post. Now I am going to do the “Show teams and players”.

I added LineUp and Player to the model:

And a view model that supports this model:

That was the easy part. The above steps are done quickly with Enterprise core objects. Good! More time left to spend in Blend (and boy will you need it!).

Start up Blend (I use Microsoft Expression Blend 3). File, Open, Project/Solution:

You can add UserControls just as you would have done in Visual studio:

So I did a user control looking like a hockey rink (took me forever!) ; that will come in handy. Doing stuff like this in Blend is just as complicated as in any other competent drawing tool (Photoshop or what have you). But Blend has an advantage with the split xaml view. You can fine tune stuff just by changing the xaml.

I then create a new WPF-Window and add my user control:

I add some comboboxes to show the lineups for each team. I also add some textblocks to show the players for each LineUp. I also add two images up on the ice, to show the team images. All of these controls should show data. So I need to bind…

   1: //This is how I bind the Image to my ViewModel

   2: <Image  x:Name="imageHome" Margin="153,111,224.54,0"

   3:     Source="{Binding Path=Class[GameDay]/Home_Image,Mode=OneWay,Converter={StaticResource ImageBlobConverter} }"

   4:     Stretch="Fill" RenderTransformOrigin="0.5,0.5" VerticalAlignment="Top" Height="107">

5:

   6: //This is how I bind one of the textblocks

   7: <TextBlock  x:Name="textBlock"

   8:         HorizontalAlignment="Left" VerticalAlignment="Bottom"

   9:     Text="{Binding Path=Class[LineUp]/CenterForward_Name}"

  10:    TextWrapping="Wrap" Margin="76.088,0,0,88.08" RenderTransformOrigin="0.515,0.055" Style="{DynamicResource playerstyle}">

11:

  12: // And the comboboxes

  13: <ComboBox DisplayMemberPath="Name"

  14:     IsSynchronizedWithCurrentItem="True"

  15:     ItemsSource="{Binding Path=Class[LineUp]}"

  16:     Height="23" Margin="225,0,140,110" Name="comboBox1" VerticalAlignment="Bottom" />

Ok, now I have said what I want to bind to, that is not enough, I need to get the data there as well.

   1: // Add a ViewModelContent component to the resource section, tell it what your ViewModel is called, and what type your EcoSpace has:

   2: <Window.Resources>

   3:     <ecoVM:ViewModelContent x:Key="VM1" ViewModelName="GameDay" EcoSpaceType="{x:Type ecospace:HockeyContEcoSpace}" ></ecoVM:ViewModelContent>

I now switch back to Visual Studio to actually put a “Game” into the GameDay ViewModel:

   1: {

   2:     public WindowGameDay()

   3:     {

   4:         this.InitializeComponent();

5:

   6:         // Insert code required on object creation below this point.

   7:     }

8:

   9:     private EcoSpace _es;

  10:     internal void SetEcoSpace(EcoSpace es, Game aGame)

  11:     {

  12:         _es = es;

  13:         (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).SetEcoSpace(_es);

  14:         (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).RootObject = aGame;

  15:         (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).GetCollectionView("LineUp").MoveCurrentToFirst();

  16:         (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).GetCollectionView("LineUpVisitor").MoveCurrentToFirst();

  17:         LayoutRoot.DataContext = Resources["VM1"];

18:

  19:     }

Notice that I expect to be handed a EcoSpace and a Game for this window to display. Also I use the method GetCollectionView of the ViewModel so that I can position the LineUp combos to show the first line up when we start.

TestRun:

Ok. Now to Animations. This is how animations work: They change a value over time, from an initial value to a desired value. Animations can be grouped together into a Storyboard.

Switching back to Blend. Go to menu Window, Workspaces, Animation:

Now your Blend workspace switch and you will see this pane at the bottom of your screen:

Use the plus sign (I marked it with red) to add a new storyboard.

PAY ATTENTION TO THE LITTLE DOT MARKED WITH GREEN!!!! When this is red – recording is on, click it to turn off recording (it toggles, so you can start and stop).

When Recording is on: WHEN YOU MOVE AROUND CONTROLS, THE NEW POSITION IS THE DESIRED POSITION FOR THE TIME INDICATED BY THE YELLOW MARKER.

Animation will make a linear move from start to goal over time (you can control this if linear is not what you want).

So this is how you go about animating the Image Opacity from 100% to 0% in 3 seconds:
- Turn recording on
- Move the Yellow time line to zero
- Set Image Opacity to 100% (you use the standard panes to set the values)
- Move the yellow line to 3
- Set Image Opacity to 0%
- Turn Animation off.

You repeat this process for all the stuff you want to move around. This is a very powerful tool and you have every chance to destroy all the work you have done so far – but it is sort of fun.

The sample now animates the Players for the selection LineUp up onto the Ice, while the team images fade out and disappear:

And when you change the Line up, the names change no matter what the current position of the animation is.

I was about to create a video to show the animation, but I went for a ClickOnce install instead:

http://www.capableobjects.com/publishedsamples/Hockey/publish.htm

Define a valid Game, then click Start…

The ViewModel

2010-01-04T23:15:00.001+01:00

In large applications with large models the UI will soon get filled with business logic that does not belong there. The logic is left there but the developer is someday going to return and clean it all up (Sure!).

Every developer knows that the degrees of freedom rapidly decrease once you fill your UI with business logic:

You cannot easily reuse the logic placed in a UI so you copy it and increase the maintenance (BAD!)
You forget about rules placed in UI so your system gets a life of its own (BAD!)
Once you have logic in the UI you cannot be expected to know it all so you get afraid to make changes to your system because something will or may break (BAD!)
You dare not give the UI to that brilliant designer because the designer will break logic for sure (BAD!)

Still I see business logic in the UI everywhere I go. When I ask about it I always get answers like: “Well this is not finished yet”, or “Well this is really special stuff, only used in one place”, or “Yea I know it sucks, I will fix that later”. But “Later” never comes, does it? It will always be just “Later”.

I am no superman for sure. I see business logic in UI I have written myself too.

If everyone or at least most of us is getting into these situations could it be that we are doing things the wrong way? Could it be that doing things the right way is just a tad bit too complicated?

These are some strategies to make developers do the correct thing and actually follow the coding guidelines:

Automated review tools like FXCop
Peer review (that usually will be done “later”)
Some other strategy that will force violators (you and me) to mend our ways – even if the correct way is really complicated (maniac team leader with rabies foam in the face)
Make it easier and faster to follow the “coding guidelines” then to be quick and dirty.

To no surprise I am in favor of making things easier. But to be able to make things easier we need to understand what cause things to go wrong in the first place: Why is the UI filling up with business logic? I think there are a couple of reasons, depending on how far you are from being model driven some of these reasons will apply:

The UI will need to transform data (could be business logic) in order to display it according to specification.
Actions performed in UI act on selections from UI-components, that has data in the transformed presentation format, and need to be transformed back (could be business logic) to model-scope in order to let the model work on the data (business logic). And you also need to check that the parameters sent to the model method are valid (could be business logic).
The existing business logic may not match 100% what your action should do, you may want to call two, three of more methods to get the job done (new business logic) and you want to do some small checks based on the results of each method (could be business logic).
Validation – your UI will do a lot of small checks to see that the data fulfills the overall rules for your application (business logic)

How do we make these reasons go away?

We do it by offering a good and easy way to transform model-elements (or data if you will) into data elements suitable for render to match the specification.
We do it by making it real easy to add business logic where it belongs (in the model), and make it easy to call it.
And we offer a clean and easy way to add validation logic.

By setting the model in focus, and making it dirt simple to add methods, derived attributes and derived associations you can do everything you need for a specific UI in the model. This is sort of a good thing . The problem is that if you have a 100 UI’s your model will get filled with 100 times x derived attributes and derived links. And that does not sound like a good thing to me. It will eventually get hard to see the trees for the forest in a model like that.

And further more when a UI is dropped and deleted for some reason, will we remember to drop the derived associations and derived attributes we added to the model to accommodate it? Probably not.

A transformation layer between the UI and the Model can fix this. The transformation layer is allowed to have business logic, as long as it is unique for the context it works on. If the logic is not unique, it should go in the model ready to be re-used. We call this transformation Layer for a ViewModel.

A ViewModel transforms a piece of the model for a specific purpose. The purpose is often, but not always, to prepare the model information for interaction with a user for a specific use case – a UI. I said often but not always; it can also be for creating data transfer objects that are suitable for exposure for another application or system, or for some reporting engine or the like.

Why is it having the rules in a ViewModel is much better than having them in the UI? There are a lot of reasons:

Testing; it is a good thing to be able to test the logic separated from the UI, because it is awkward and error prone to test and read the results back from the UI.
ViewModel re-use ; you may have different UI’s for the exact same use case (beginner/advanced, Web-api/Rich client etc).
Design time type checking; most UI-binding strategies rely on using strings that can only be checked at runtime (true for winforms, WPF, Silverlight and ASP.NET), whereas a good ViewModel is type checked at design or compile time.
The designer working on the UI can harm important logic if the logic is in the UI.
If we have dedicated designers we will not want to wait for them to release a UI file in order to fix business logic within.
The UI may be on the other side of a network (another physical tier) so the UI cannot have access to the domain layer tier
UI and logic have very different motivators and hence will often change for different reasons (looking good versus working correctly), mixing them up add confusion regarding the distinction between these important aspects.
Security, designer that get access to the ViewModel cannot go beyond the ViewModel and unintentionally expose information that should not get exposed in the use case at hand.

The thing is that you do not have to use a ViewModel pattern to create a great application, it is just that is a good idea to use the ViewModel pattern when building applications that are going to be worked on for a long time, released in several versions over several iterations, and will most likely see different developers and UI-designer, and may very well be radically changed with regards to presentation framework during its lifespan. In short – it is always a good idea for successful applications to use a ViewModel pattern.

The declarative ViewModel

Presented with a model that I got from Rick Weyrauch, that incidentally helps out as a Hockey Referee when he is not coding, I wanted to create a ViewModel for the use-case “Set up new Hockey game”.

The Game class has a state machine:

I took a piece of paper and draw the UI I wanted to achieve:

Now I know what the requirements are on the ViewModel since I can see from the drawing what data the ViewModel needs to hold.

And then created this ViewModel That I named GameSetup:

Notice that it is just a series of named ocl expressions. Some expressions are nested to other list definitions like Home_PickList that states that if the Game has a picked GameType, then we know what teams that can be picked – namely those teams that are associated to that GameType

I created some test data so that UI can show something:

   1: private Game CreateSomeTestData()

   2: {

   3:     // Game types

   4:     var gtboys15 = new GameType(_es) { Name = "15 years, Boys" };

   5:     var gtboys16 = new GameType(_es) { Name = "16 years, Boys" };

   6:     var gtgirls15 = new GameType(_es) { Name = "15 years, Girls" };

7:

   8:     // team types

   9:     var ttb15=new TeamType(_es) { Name = "Boys 15 years" };

  10:     var ttb16 = new TeamType(_es) { Name = "Boys 16 years" };

  11:     var ttg15 = new TeamType(_es) { Name = "Girls 15 years" };

12:

  13:     // Valid team-game combinations

  14:     gtgirls15.TeamTypes.Add(ttg15);

15:

  16:     gtboys15.TeamTypes.Add(ttb15);

  17:     gtboys15.TeamTypes.Add(ttg15); // girls can play in boys 15 year

  18:     gtboys16.TeamTypes.Add(ttb15); // 15 year boys can enter 16 year games

  19:     gtboys16.TeamTypes.Add(ttb16);

  20:     gtboys16.TeamTypes.Add(ttg15); // girls can play in boys 16 year

21:

22:

23:

  24:     new Team(_es) { Name = "Brynäs",Image=GetImage(imagebrynäs), TeamType=ttb15 };

  25:     new Team(_es) { Name = "Brynäs", Image = GetImage(imagebrynäs), TeamType = ttb16 };

  26:     new Team(_es) { Name = "Brynäs", Image = GetImage(imagebrynäs), TeamType = ttg15 };

27:

  28:     new Team(_es) { Name = "Luleå", Image = GetImage(imageluleå), TeamType = ttb15 };

  29:     new Team(_es) { Name = "Luleå", Image = GetImage(imageluleå), TeamType = ttb16 };

  30:     new Team(_es) { Name = "Luleå", Image = GetImage(imageluleå), TeamType = ttg15 };

31:

  32:     new Team(_es) { Name = "Djurgården", Image = GetImage(imagedjurgården), TeamType = ttb15  };

  33:     new Team(_es) { Name = "Djurgården", Image = GetImage(imagedjurgården), TeamType = ttb16 };

  34:     new Team(_es) { Name = "Djurgården", Image = GetImage(imagedjurgården), TeamType = ttg15 };

35:

  36:     return new Game(_es)

  37:     {

  38:         ScheduledDate = DateTime.Now

  39:     };

40:

  41: }

Now I am ready to build the UI.

   1: <Window x:Class="WPFBinding.Window2"

   2:     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

   3:     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

   4:     xmlns:eco="clr-namespace:Eco.WPF;assembly=Eco.WPF"

   5:     xmlns:ecoVM="clr-namespace:Eco.ViewModel.WPF;assembly=Eco.WPF"

   6:     xmlns:Controls="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit"

   7:     xmlns:local="clr-namespace:WPFBinding"

   8:     xmlns:ecospace="clr-namespace:WPFBinding;assembly=WPFBinding.EcoSpace"

   9:     Title="Window2" Height="300" Width="500" >

  10:     <Window.Resources>

  11:         <ecoVM:ViewModelContent x:Key="VM1" ViewModelName="GameSetup" EcoSpaceType="{x:Type ecospace:WPFBindingEcoSpace}" ></ecoVM:ViewModelContent>

  12:         <local:ImageBlobConverter x:Key="ImageBlobConverter"/>

  13:     </Window.Resources>

  14:     <Grid>

  15:         <Grid Name="vmrootStackPanel" DataContext="{StaticResource VM1}">

  16:             <Grid.ColumnDefinitions>

  17:                 <ColumnDefinition></ColumnDefinition>

  18:                 <ColumnDefinition></ColumnDefinition>

  19:                 <ColumnDefinition Width="50"></ColumnDefinition>

  20:             </Grid.ColumnDefinitions>

  21:             <Grid.RowDefinitions>

  22:                 <RowDefinition></RowDefinition>

  23:                 <RowDefinition></RowDefinition>

  24:                 <RowDefinition></RowDefinition>

  25:                 <RowDefinition></RowDefinition>

  26:                 <RowDefinition></RowDefinition>

  27:                 <RowDefinition></RowDefinition>

  28:                 <RowDefinition></RowDefinition>

  29:                 <RowDefinition></RowDefinition>

  30:             </Grid.RowDefinitions>

31:

  32:             <TextBlock Grid.Row="0" Grid.Column="0" Text="GAME : " HorizontalAlignment="Right" ></TextBlock>

  33:             <TextBox Grid.Row="0" Grid.Column="1" Text="{Binding  Path=Class[GameSetup]/Presentation,Mode=OneWay}"></TextBox>

34:

  35:             <TextBlock Grid.Row="1" Grid.Column="0" Text="Type of game : " HorizontalAlignment="Right" ></TextBlock>

  36:             <ComboBox Grid.Row="1" Grid.Column="1"  DisplayMemberPath="Name"  ItemsSource="{Binding Path=Class[GameType_PickListPresentation]}" SelectedValuePath="self"  SelectedValue="{Binding Path=Class[GameSetup]/GameType}"  ></ComboBox>

37:

  38:             <TextBlock Grid.Row="2" Grid.Column="0" Text="Home team : " HorizontalAlignment="Right" ></TextBlock>

  39:             <ComboBox Grid.Row="2" Grid.Column="1"  DisplayMemberPath="Name"  ItemsSource="{Binding Path=Class[Home_PickListPresentation]}" SelectedValuePath="self"  SelectedValue="{Binding Path=Class[GameSetup]/Home}"></ComboBox>

  40:             <Image Grid.Row="2" Grid.Column="2"  Source="{Binding Path=Class[GameSetup]/Home_Image,Mode=OneWay,Converter={StaticResource ImageBlobConverter} }"></Image>

41:

42:

  43:             <TextBlock Grid.Row="3" Grid.Column="0" Text="Visitor team : " HorizontalAlignment="Right" ></TextBlock>

  44:             <ComboBox Grid.Row="3" Grid.Column="1"  DisplayMemberPath="Name"  ItemsSource="{Binding Path=Class[Visitor_PickListPresentation]}" SelectedValuePath="self"  SelectedValue="{Binding Path=Class[GameSetup]/Visitor}"></ComboBox>

  45:             <Image Grid.Row="3" Grid.Column="2"  Source="{Binding Path=Class[GameSetup]/Visitor_Image,Mode=OneWay,Converter={StaticResource ImageBlobConverter} }"></Image>

46:

  47:             <TextBlock Grid.Row="4" Grid.Column="0" Text="Scheduled date : " HorizontalAlignment="Right" ></TextBlock>

  48:             <Controls:DatePicker Grid.Row="4" Grid.Column="1"  ></Controls:DatePicker>

49:

  50:             <Button Grid.Row="5" Grid.Column="0" IsEnabled="{Binding Path=Class[GameSetup]/CanStartGame}" Click="ButtonStartGame_Click">

  51:                 <TextBlock Text="Start Game"></TextBlock>

  52:             </Button>

53:

  54:             <Button  Grid.Row="5" Grid.Column="1"  IsEnabled="{Binding Path=Class[GameSetup]/CanEndGame}" >

  55:                 <TextBlock Text="End Game" ></TextBlock>

  56:             </Button>

57:

  58:         </Grid>

  59:          <StackPanel Orientation="Horizontal" VerticalAlignment="Bottom">

  60:             <Image Height="50" Name="imagebrynäs" Stretch="Fill" Width="50" Source="/WPFBinding;component/brynäs.jpg" />

  61:             <Image Height="50" Name="imagedjurgården" Stretch="Fill" Width="50" Source="/WPFBinding;component/djurgården.jpg" />

  62:             <Image Height="50" Name="imageluleå" Stretch="Fill" Width="50" Source="/WPFBinding;component/Luleå.jpg" />

  63:         </StackPanel>

  64:     </Grid>

  65: </Window>

What happens in the xaml above is that we have a ViewModelContent component in the resource section. We initiate it to the name of the ViewModel, and we also provide the Type of the ecospace.

The ViewModelContent object, now keyed as VM1, is put in the DataContext of the Grid where I place the UI components. If a WPF Binding does not get an explicit source it will use whatever it finds in the DataContext (the datacontext is propagated down the logical tree, so for us it is everywhere).

In code behind we hook up the EcoSpace and the rootobject-property (dependencyproperty so that you bind as target and as source) to our demo Game object:

   1: (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).SetEcoSpace(_es);

2:

   3: (Resources["VM1"] as Eco.ViewModel.WPF.ViewModelContent).RootObject=CreateSomeTestData();

The UI looks like this:

Yes it looks bad; but hey, you can hand it to any WPF savvy designer in the world – the data and the rules are safe in the ViewModel.

It already shows some of the good effects of separating UI from logic. If you run the sample you will see and hopefully appreciate that:

The PickLists for Home and Visitor are filtered based on Type of Game
The Picklist for Home team filters away the Visitor team if set (and vice versa)
Start game is enabled only after both home and visitor are set
The End game button is disabled until the Game is started

These are some examples of business logic that would have easily ended up in the UI if we did not have a good place to define it.

Taking it further still

If the cost of creating and maintaining a ViewModel is high fewer ViewModels will be created. So our mission is to reduce the cost of creating and maintaining them. Can we do more? I will argue that we can.

WPF is a declarative way to describe the UI. This mean that the same basic lookless components like TextBlock, TextBox, CheckBox, Combobox and Image etc will be used again and again and they will be given a look by an external style or template.

What if we use this fact and provide some basic rendering/placing hints for the ViewModel columns? We could then use those clues to spill out the correct lookless control in the intended relative position so we would not need to mess about with xaml every 5 minutes… I am excited… Xaml is a bit too scripty for my old strongly typed ways…

This is what the ViewModel-Editor looks like without rendering hints:

And this is the way it looks when I have checked the “Use Placing Hints” checkbox:

Given the extra fields for “Presentation”, “Column”,”Row”,”Span” etc I can work the ViewModel - preview to look like this:

Now I really need to stress this so that I do not get misunderstood: We do not mix presentation with UI, we do however allow for adding optional placing hints or clues on what you have in mind while designing the ViewModel.

Having a ViewModel with placing hints, you can add a ViewModelWPFUserControl to your form with just one row:

   1: <ecoVM:ViewModelWPFUserControl Grid.Row="2" x:Name="VMU1" EcoSpaceType="{x:Type ecospace:WPFBindingEcoSpace}" ViewModelName="GameSetup" ></ecoVM:ViewModelWPFUserControl>

And the result is:

And remember that these auto layouted controls also adheres to external set styles. (Notice the datetime picker is gone? Datetime picker is in WPFToolkit so we do not use it by default. Implement ViewModelWPFUserControl.OnColumnUIOverride to add your own components to its layout engine.)

Summing it up

This has been a brief overview of the ViewModel concept. Things intentionally left out for now was Actions, Validation-rules, Variables, Master-detail (since there were no details in the sample ), Style references and Tab order.

I have written about the benefits of having a ViewModel in the first place. Then I wrote about the Modlr approach with a strictly declarative ViewModel. We looked at the sample using such a ViewModel and some of the effects it gave in separating logic from UI. Then I showed you a ViewModel with placing hints – a bit un-orthodox for sure, but efficient and easy to maintain.

Thanks goes out to everyone that has been involved in the Modlr ViewModel approach by giving feedback, and to Rick for providing the sample model – Hope I did not abuse it.

Knowing nothing, where to begin

2009-12-21T15:07:00.001+01:00

When you are dropped by parachute deep behind enemy lines with nothing but your analytical skills – where do you start? Ok, I probably should not compare the client and their business with hostile territory filled with enemies. Sorry! But still! Where do you start if you know nothing?

You say “Hi!” to everyone, exercise your complete toolbox of people skills, follow everyone to lunch, buy the informal leaders beer etc… But that is not enough is it?

Being a developer using ECO and the strategies proposed by DDD I will know what to do once I know what “the whole thing is about”. But the client is not really equipped to tell me what I need to know spontaneously, so I need some strategy to get that information extracted from them.

This post is about that strategy. Ok, I know there must be like a million ideas on how this is done. This is the way we do it:

Gather a representative group of people from the domain
Set up a workshop and let them brainstorm on who is showing any interest at all in what they do. More specifically ask them: who calls you on the phone, who emails you, who comes to visit, who delivers stuff, who sends you stuff, who buys your stuff, etc. All these questions are reversible: Who do you call, Who do you email etc. Collect this information and keep it as the Triggers.
For each unique persona from step 2 find out what the goal of this persona is; why does X email you, what is their goal? Why do you email that person, what is your goal? Collect this information and keep it as the Goals.
Split your group into smaller groups and let them break down each non-nonsense combination of trigger and goal into some steps that are central in getting to the goal. Make them aim for 5 steps. If they have a hard time getting started, encourage them to bring up just 1 step. Example: “Trigger is Customer, Goal is Getting a loaf of bread”. One obvious step is “handing the bread to the customer”. Great! Now force your group to explain what they do before- , and what they do after that step. “Need to fetch the bread from the shelf” is before, and “Receive payment” is after. This is going great! Continue like this, and throw away the silly steps and keep the important steps. What they create here are overviews of what their business is about. Keep this information as Processes.

After you are thru these steps you will have a pretty good idea on what you are up against. You will have a set of high level processes. Document these in Gaffr.net or ECO:

Some processes that you have already found might be detailing processes for a another process. And some steps in a found process might need detailing in further steps; you should callback your domain group to help you out with that.

By arranging the processes as “detailing” a step, you build up a structure in the Modlr tree:

Do you really need to involve real domain people? Will it not suffice with reading some existing documentation and talking to some IT-guys in the company? No. It will not suffice for 2 major reasons:

You do not know what the real issue is – it might be that the current documentation and or the current IT-crew is wrong.
You really need to get real people involved so that they feel and know that you are on their side. After all you will be a central player when it comes to change of these peoples working environment. You need to earn trust, you need to communicate, you need to make them involved. If you do not you will have a hell of a time trying to get the real people to understand the greatness of your work once you are done. And then it is all for nothing.

When you have reach this far you need to start on the information model. Create 1 class diagram per process and associate the two:

As you focus on a specific process when creating this class diagram you get a small and readable result:

The Process diagrams indicate that they are associated to class diagrams, and you can click the Icon to jump straight to the class diagram:

Further more the Process tree gives you a good structure of diagrams:

Now you have the big picture on “What it is that happens” from the processes, you get the “What information” view from the class diagrams. All you need now is the detailed business rules that controls this process. Being totally into declarative development, I only consider for short while to actually start to write c# code to catch these. But the state diagrams are better because the documentation gets clearer and maintenance will be cheaper in that form (our point of view). You can associate these to processes as well:

Once you have reached this far you may want to take it yet another step: Declare a viewmodel per process… But I will save ViewModels for another post.

Summing it up

The process tree will give you a navigation of diagrams and artifacts. The processes will make it easier for an outsider to understand the domain. And if you are a group of people where some do client communication with process modeling and some take it further with development you can now share one tool to keep your development efforts collected.

Weather you choose to do everything in your development declarative as we do, or only part of your your work declaratively and the rest by traditional coding is entirely up to you.

Total cost of using Gaffr.net

If you control your own method and you think that Gaffr.net fits, you can even license Gaffr.net; we will stripe it so your clients see your logos and they need not to know anything about us. You will then both have a tool and method. You will be free to price the tool as you see fit and the payment models are up to discussion but very modern and flexible. Email us today: sales at capableobjects.com .

Catching more information in your model

2009-12-06T16:53:00.001+01:00

Once you have started to travel the path of Model driven development you might find that the declarative approach is useful for even more things than what you thought of at first.

You may find yourself searching for a way to mark up certain classes as UserFriendly or an association as being HeavyToLoad, so that your code can see this and perform differently. Of course you can create code that checks if it used on a particular class or on a particular association, but that will eventually cost you in more maintenance.

We cannot and should not try to understand your future needs, after all you probably do not even know yourself yet. So what to do… Tag extensions…

Tag extensions definition

Brings up this dialog

You can create new extensions. In the example above there are 3 extensions, Kasper.Seeker, EcoExtensions and Kasper.

Each extension has a number of TagTypes – on the example above the Kasper extension has 4 tag types; Kasper.AutoSeekAndPick, Kasper.AllowUserNew, Kasper.UserFriendlyClass, Kasper.BusinessDeleteValue.

Each TagType is applicable to only one type of “TagExtendableItem” in the item. In the example above the Kasper.BusinessDeleteValue is active on Association end points.

A TagType can be made to act as a enumerable valueset, the example above allows for 4 values; PSCheckMustBeEmpty, MustBeEmpty, OkEvenIfNotEmpty and NoOneHasMadeADescisionForThisYet.

Tag extension usage

Once you have defined the tag extensions the property inspector is updated.

The Extensions shows up as any other properties of your modeled elements.

The values of the tag extensions are stored as tagged values and translated into .net code attributes in the generated code:

   1: [UmlElement("AssociationEnd", Id="31cfadd7-2b04-493c-a5e5-399913764949", Index=Eco_LoopbackIndices.Reserverad)]

   2: [UmlMetaAttribute("association", typeof(KasperPackage.LagerrorelsePrioriteringLagerrorelsePrioriteringarAnvandareReserverad), Index=1)]

   3: [UmlMetaAttribute("multiplicity", "0..1")]

   4: [UmlTaggedValue("Kasper.BusinessDeleteValue", "OkEvenIfNotEmpty")]

   5: public Anvandare Reserverad {

   6:   get {

   7:     return ((Anvandare)(this.eco_Content.get_MemberByIndex(Eco_LoopbackIndices.Reserverad)));

   8:   }

   9:   set {

  10:     this.eco_Content.set_MemberByIndex(Eco_LoopbackIndices.Reserverad, ((object)(value)));

  11:   }

  12: }

And you can access it in your code, either by using standard .net approaches to get to code attributes, or by using the extended meta information that ECO brings.

   1: foreach (IStructuralFeature sf in TheObject.AsIObject().UmlClass.AllStructuralFeatures)

   2: {

   3:   if (sf is IAssociationEnd)

   4:   {

   5:     IAssociationEnd ae = (sf as IAssociationEnd);

   6:     string tv = ae.TaggedValues.ValueForTag("Kasper.BusinessDeleteValue", "NoOneHasMadeADecisionForThis");

   7:     if (tv == "PSCheckMustBeEmpty" || tv == "NoOneHasMadeADecisionForThis" && !(ae.DeleteAction == DeleteAction.Prohibit))

8:

Tag extension visualization

Even if the Tag extensions has been in ECO and Gaffr.net for some time, a new way in how they can be displayed has been added recently. A new tab on the TagExtension dialog called Symbols has been added:

In this dialog you can define symbols that are built up by a piece of xaml:

   1: <Rectangle xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' Fill='Blue' Width='16' Height='16'>

   2:   <Rectangle.RenderTransform>

   3:    <RotateTransform Angle='45'/>

   4:    </Rectangle.RenderTransform>

   5: </Rectangle>

Any stand alone xaml is valid to use here so you can define any kind of symbol you want.

You can then associate the TagTypeValues to a symbol:

And then your diagram displays the symbols when the values are set:

When hovering over a symbol, you get a tooltip that explains what tag extension it is and what the value is.

So start decorating your business models. Move stuff from your memory to Modlr for more people to see and for you to relax. Remember that development is still the hardest thing in world to truly master so accept any help you can get.

Derived attributes & associations

2009-11-15T11:58:00.001+01:00

Derived attributes has been in ECO for ages . To a SQL-guy derived attributes resemble calculated fields. Derived attributes are just like calculated fields that subscribe to all the values that it is calculated from. So whenever data, seen by the expression, is changed the derived attribute is marked as out of date. And the next time you or your UI tries to read it, the attribute is re-evaluated.

The key thing with derived attributes is that it is NOT calculated each time you access the attribute. If it were performance would suffer. It is calculated (or derived) as few times as theoretical possibly; only when read the first time after a change of anything that the derivation expression looks at.

The concept of derivation relies on the concept of subscription – everything in your domain layer has the ability to signal whenever it is changed (the publisher pattern), and subscribers subscribe to publishers to detect these changes. Although this is a different story I must mention that publishing events to catch changes is a key difference between the ECO approach to implementing a domain layer and the POCO way (plain old c#-objects) like NHibernate and some other frameworks use.

Having a model as the one above I can create a derived attribute on the Order that calculates the total shipping cost by checking the products ordered and the customer’s country in OCL:

self.OrderItems->FilterOnType(ProductThatNeedsShipping).Weight->sum

 * self.Customer.Country.CostToShipHerePerKilogram

I do this by creating a new Attribute, set the AttributeMode to Derived and fill in the DerivationOCL.

Derived attributes can be used in other derivation expressions so I can make a derived TotalCost without repeating the definition of the Shipping cost:

self.OrderItems.Product.Price->Sum() + self.ShippingCost

The expression of derived attributes can be expressed with C# / VB.NET / Delphi.NET code instead of in OCL (ECO only, not Gaffr.net). You do this by setting the AttributeMode to Derived as before but leave the DerivationOCL property empty. Generate code and inspect the Order.eco.cs file. At the bottom of the file you will see these stubs:

   1: /// <summary>This method is called when ShippingCost needs to be calculated</summary>

   2: partial void ShippingCostDerive(ref string res);

3:

   4: /// <summary>This method is called when TotalCost needs to be calculated</summary>

   5: partial void TotalCostDerive(ref bool res);

You never change the files named something.eco.cs – instead you implement these partial methods in the file something.cs (or vb or delphi). So in our case we open up the Order.cs file and enter:

   1: partial void ShippingCostDerive(ref double res)

   2: {

   3:     res=0;

   4:     double totWeight=0;

   5:     foreach(OrderItem i in OrderItems)

   6:     {

   7:         if (i is ProductThatNeedsShipping)

   8:         {

   9:           totWeight += (i as ProductThatNeedsShipping).Weight;

  10:         }

  11:     }

  12:     if (Customer!=null && Customer.Country!=null)

  13:       res = totWeight * Customer.Country.CostToShipHerePerKilogram;

  14: }

Prior to ECO5 you needed to explicitly explain to ECO what ECO should subscribe to in order to stay updated if anything changes. But as of the introduction of the IAutoSubscriptionService this is no longer necessary.

The IAutoSubscribeService deserves a chapter of its own but here is a brief overview:

The caller of your code derivation has a subscriber and starts an Auto subscription session. An Auto subscription session is notified about all access to the domain layer as long as the session is in effect. All access is inspected and builds up the description of what ECO needs to subscribe to in order to know when to mark the attribute out of date. The session is ended after your code derivation returns.

Conceptually this is what happens:

   1: using (this.AsIObject().ServiceProvider.GetEcoService<IAutoSubscriptionService>().StartSubscribe(subscriber))

   2: {

   3:    double res;

   4:    this.ShippingCostDerive(ref res)

   5: }

All you need to remember

All you need to remember is that derived attributes can be defined in code or in the model with OCL. Derived attributes are efficient and always return the correct up to date result. Associations can also be derived the same way as attributes.

In the example model above the Shipping cost is out of date if you add a new orderline, if you change the customer, if the customer changes country, if a already picked ProductThatNeedsShipping gets an updated weight etc – it covers every and any change that effects the calculation as long as that change is part of your domain layer.

I hope that you see the positive effect this will have on your UI implementations – Showing the ShippingCost and see it update as you change anything it depends on by one central definition far away from the UI.

Using derived attributes and associations clean up your code and consolidates central definitions to single points and thus greatly reduce maintenance costs and efforts.

Segmenting definition and logic

2009-10-26T18:30:00.001+01:00

ECO makes it easy to define models. To reuse a model you can simply import a ecopkg.

This will make the package part of your model and you can edit the contents of the package. Code generation will also create new code and empty stubs for code implemented operations.

Normally you want to reuse the whole model assembly that may contain code implemented operations, maybe code derived attributes and relations and so on.

To do this you choose the “Edit referenced packages” option instead:

Then choose “Add” and find a ecopkg you want to use as part of your complete model:

In this post I choose the EcoAspProvider.ecopkg that comes with the ECO install. This package implements the membership functions for ASP.NET as eco objects.

When referencing a package like this, the classes in the package are made read only. You can still draw associations to and from the classes in referenced packages as long as the association end is not embedded in any read only end. In other words: you can point out read only classes, but you cannot make a read only class point out anything new. Give this some thought and you will probably find it very intuitive; the external, referenced, definition cannot be changed in this context.

A referenced package is NOT code generated with the rest of the model. The referenced package probably comes with a compiled assembly or project of its own that use the definition in runtime. Add a reference to this as you would do with any other externally defined logic in .net:

If you try to change a property of a referred package ECO will stop you:

To make your solution use the referred package you must click the choose package icon in the ecospace designer:

Then make sure that all packages you want to use are selected:

Then make sure you generate code and build your solution before you generate the schema (the schema is derived from the runtime model that is derived by looking on the code alone)