You can add HiddenField to the Gridview like that:
<asp:GridView ID="grdVw" runat="server" AutoGenerateColumns="false"> <Columns> <asp:TemplateField> <ItemTemplate> <asp:HiddenField ID="hdnID" runat="server" Value='<%# Bind("ID") %>' /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView>
And you can get the HiddenField Value in C# as below:
comboBoxID.SelectedValue = ((HiddenField)grdVw.SelectedRow.Cells[0].FindControl("hdnID").Value;