Thanks for your prompt response.
I would like to get the current item in the combobox, in the RowValidating event.
I saw the extension methods, but can't get an instance of the combobox:
sender, GridViewRowValidatingEventArgs e)
GridViewRow validatingRow = e.Row;
RadComboBox projectSubjectCmb = validatingRow.ChildrenOfType<RadComboBox>().FirstOrDefault();
//projectSubjectCmb is always null
fooEntity selectedFoo = projectSubjectCmb.SelectedItem
//my validation logic continues.....