DomainDataSource Extension Methods
To add a new item or edit an existing item in the DomainDataSource that ships with the .NET RIA Services, you must first cast the DataView property to an IEditableCollectionView. Jeff Handley does a good job of explaining the reason for this in his DomainDataSource.DataView post.
Silverlight 3 Breaking Changes
I have been reading up on the new features in Silverlight 3 over the last couple of days, and have often been confused because what I was reading didn’t line up with what I was seeing. It appears many of the articles and videos that are currently available have been created against the Silverlight 3 Beta version, and a number of changes have been made between the Beta and final release. For example, the DataForm control is often mentioned as being in the System.Windows.Controls.Data.DataForm.dll assembly, but has actually been moved from the Silverlight SDK into the Silverlight Toolkit.