>Do you stop getting the error when you remove the code for hiding it?

yes . if i comment out

Datacolumn1.Hidden = True

it works fine.

Hi, i build it dynamic. on the aspx page i have only
  <ig:WebDataGrid ID="WebDataGrid1" runat="server" Height="500px" Width="98%" AutoGenerateColumns="false" >
                             <Behaviors>
                              <ig:Selection RowSelectType="Multiple" Enabled="true" />
                              <ig:RowSelectors RowNumbering="true" Enabled="true" />
                           
        <ig:Paging PagerAppearance="Bottom" PageSize="10" PagerCssClass="igg_CustomPager"
         Enabled="true">
         <PagerTemplate>
            <uc1:CustomerPagerControl ID="CustomerPagerControl1" runat="server" />
         </PagerTemplate>
        </ig:Paging>
       </Behaviors>
   
   
    </ig:WebDataGrid>

code behind i have

           Dim Datacolumn1 As New BoundDataField
                Datacolumn1.DataFieldName = "L_ID"
                Datacolumn1.Key = "L_ID"
                Datacolumn1.Header.Text = "L_ID"
   >>>>>             '  Datacolumn1.Hidden = True

                WebDataGrid1.Columns.Add(Datacolumn1)

                Dim Datacolumn2 As New BoundDataField
                Datacolumn2.DataFieldName = "test2"
                Datacolumn2.Key = "test2"
                Datacolumn2.Header.Text = "test2."
                Datacolumn2.Width = 10 * 8
                'http://alexonasp.net/samples/stringformatting/
                Datacolumn2.DataFormatString = "{0:MM/dd/yyyy}"
                WebDataGrid1.Columns.Add(Datacolumn2)

                Dim Datacolumn3 As New BoundDataField
                Datacolumn3.DataFieldName = "test3"
                Datacolumn3.Key = "test3"
                Datacolumn3.Header.Text = "test3"
                WebDataGrid1.Columns.Add(Datacolumn3)

WebDataGrid1.DataSource = MyRS

WebDataGrid1.DataBind()