Does not matter what value is set to the Connection's StartCap/EndCap properties, the ends of the connection are rendered as if the value of these properties is "None".
When you use the ConnectionDataSource of RadDiagram to data bind an SqlDataSource to its connections, a NullReferenceException is thrown. You can avoid this issue by using ConnectionDataSourceId instead.
When you change the beginning or the end of an existing RadDiagram connection and call the client-side save() method, the exported data for the modified connection will not be updated.
RadDiagram throws a NullReferenceException when you bind it declaratively and place it in the ItemTemplate of a data bound control, for example a Repeater.