I would love to just write NONE here but no…
When using many to many associations like:
It will fail adding to this association in Silverlight.
Reason: This construct creates an implicit link class (FriendExpensiveStuff) and the implicit class is created with reflection things not available in Silverlight.
The workaround is to create an explicit link class like this:
Then it works in Silverlight.
And frankly you will probably have the need for the explicit link class anyway: