I've never been a great fan of the point and click nature of the DataGrid in .Net, it all seams too easy and there was always the problem with the bloat that was the ViewState.
I'm having to put together a quick proto-type atm so I'm just dragging and dropping controls as fast as my little mouse can go ;). I hit a problem when I was trying to update a GUID though the Edit / Update.
The problem is not with the DataGrid itself but with the underlying DataSource. The problem is that is by default the dataset asp:parameters convert any GUID (uniqueidentifier in SQL) to a object type.
1 <asp:SqlDataSource ...>
2 <InsertParameters>
3 <asp:Parameter Name="UserId" Type="Object" />
4 ...
5 </InsertParameters>
6 </asp:SqlDataSource>
This is a bug that was noted in Beta 2 but got in to production. The work around is if you remove the Type="Object" then it work.
1 <asp:SqlDataSource ...>
2 <InsertParameters>
3 <asp:Parameter Name="UserId" Type="Object" />
4 ...
5 </InsertParameters>
6 </asp:SqlDataSource>