Есть 
<Columns> ...
               <asp:TemplateField HeaderText="test" SortExpression="column"> ... 
                        <EditItemTemplate>

                    <asp:DropDownList ID="hello" runat="server" AutoPostBack="True" SelectedValue='<%# Bind ("column") %>'>
                       
                                  <asp:ListItem Selected="True">hi</asp:ListItem>
                   
                      </asp:DropDownList></EditItemTemplate></asp:TemplateField></Columns>

Выдает : 

'hello' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value 

без SelectedValue - NULL :

Cannot insert the value NULL into column 'column', table 'myBase.dbo.column'; column does not allow nulls. UPDATE fails.
The statement has been terminated.