Something like this - though I've not tested it

IEcoServiceProvider sp = MyEcoSpace or EcoServiceProvider
ITypeSystemService ts = sp.GetEcoService<ITypeSystemService>();
IClass class = ts.TypeSystem.AllClasses.GetItemByName("Class1");

foreach (IStructuralFeature sf in class.AllStructuralFeatures)
{
 if (sf.FeatureType == FeatureType.AssociationEnd)
 {
  if ((sf as IAssociationEnd).Type_.Name == "Class2")
  {
   //Code Here
  }
 }
}

Regards

Nick