Ok, this post is only a half post, as for now I will leave out a lot of details. I use Telerik's control suite for ASP.Net (www.telerik.com) at work. I spent about four hours yesterday trying to get a RadComboBox's selected value to bind to a column in the Grid's dataset when in edit mode (so I could get two way databinding on the grid so it will handle the update/delete/insert automatically as long as you setup the appropriate procs and params in your SQL datasource).
Without including all the details I couldn't get things to work until I bound the RadComboBox to a column that initially had the value of ''in the dataset . Then, in the item data bound event I set the value the RadComboBox to the value it should be.
So in my stored proc I had to return two columns like this, mycolumn (which I set in the select to ''), and then mycolumn_real_value which in the stored proc is the value that should be the value for mycolmn. The RadComboBox's selectedvalue is bound to mycolumn like selectedvalue='<%# Bind("mycolumn") %>'. Then in the item data bound event for the Grid I cast the e.Item as a GridItem, then do a findcontrol to find the RadComboBox, then set the text of that RadComboBox to the value of mycolumn_real_value. Also you can't give the RadComboBox a DataSourceID. I ended up building a function that pulls a new DataView out of a DataSource, then loops through that view's rows and add's new items to the RadComboBox.
I'm sure there is another way, but I couldn't get anything else to work, including the downloaded Telerik examples.
I'll post actual code for this at one point, and to 99% of you who read this it will sound like a bunch of nonsense(like most of my post), but to those of you like me who have been pulling their hair out to get two way databinding to work on a RadComboBox in a RadGrid the above will put you on the right path.