Hi Lyuba, (juhu it works)
if i write
Datacolumn1.Header.CssClass = "hidden"
Datacolumn1.CssClass ="hidden"

is important because of the header will display but not the column. if i write both , both is hidden, the complete column is hidden:)
many thanks for the help

>if it is possible for you to attach a sample in the support ticket that you created it would be very nice

i think if you simple write .hidden=false everyone can reproduce the error. hope you can fix it
thanks martin

Hello Martin,

I have built small sample based on provided details by you. I am not able to replicate the described issue.  Could you have a look at it please?  You can download it from the current post.

In the  sample I am using your code as much as possible. 

aspx  markup :

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
          
            <ig:WebDataGrid ID="WebDataGrid1" 

                runat="server" 

                Height="350px" 

                Width="98%" 

                AutoGenerateColumns="false">
                <Behaviors>
                    <ig:Selection RowSelectType="Multiple" 

                    CellClickAction="Row" Enabled="true" />
                    <ig:RowSelectors RowNumbering="true" 

                    Enabled="true" />
                </Behaviors>
            </ig:WebDataGrid>
       
        </ContentTemplate>
    </asp:UpdatePanel>

Code file:

  if (!Page.IsPostBack)
        {

            //Add behavior
            this.WebDataGrid1.Behaviors.CreateBehavior<Paging>();
            //Handle PageIndexChanged event
            this.WebDataGrid1.Behaviors.Paging.PagingClientEvents
           .PageIndexChanged = "WebDataGrid1_PageIndexChanged";

            BoundDataField Datacolumn1 = new BoundDataField();
            Datacolumn1.DataFieldName = "id";
            Datacolumn1.Key = "id";
            Datacolumn1.Header.Text = "id";
            Datacolumn1.Hidden = true;
            WebDataGrid1.Columns.Add(Datacolumn1);

            Datacolumn1 = new BoundDataField();
            Datacolumn1.DataFieldName = "Item";
            Datacolumn1.Key = "Item";
            Datacolumn1.Header.Text = "Item";
            Datacolumn1.Hidden = false;
            WebDataGrid1.Columns.Add(Datacolumn1);

            Datacolumn1 = new BoundDataField();
            Datacolumn1.DataFieldName = "Data";
            Datacolumn1.Key = "Data";
            Datacolumn1.Header.Text = "Data";
            Datacolumn1.Hidden = false;
            WebDataGrid1.Columns.Add(Datacolumn1);
        }
        WebDataGrid1.DataSource = this.MakeTable();

        WebDataGrid1.DataBind();

        this.WebDataGrid1.Behaviors.Paging.PagerTemplate = new CustomPagerTemplate();

Datacolumn1.Hidden = true;
            WebDataGrid1.Columns.Add(Datacolumn1);

            Datacolumn1 = new BoundDataField();
            Datacolumn1.DataFieldName = "Item";
            Datacolumn1.Key = "Item";
            Datacolumn1.Header.Text = "Item";
            Datacolumn1.Hidden = false;
            WebDataGrid1.Columns.Add(Datacolumn1);

            Datacolumn1 = new BoundDataField();
            Datacolumn1.DataFieldName = "Data";
            Datacolumn1.Key = "Data";
            Datacolumn1.Header.Text = "Data";
            Datacolumn1.Hidden = false;
            WebDataGrid1.Columns.Add(Datacolumn1);
        }
        WebDataGrid1.DataSource = this.MakeTable();

        WebDataGrid1.DataBind();

        this.WebDataGrid1.Behaviors.Paging.PagerTemplate = new CustomPagerTemplate();

As you can see I hide the first column as you suggested. 

Let me know what I am missing in this sample to get the error. 

Hi,

i have the same error in WebDataGrid when i hide a column like this:

<

ig:BoundDataField DataFieldName="AufLiefPosId" DataType="System.Int32" Hidden="true" Key="PosId" Width="50px">

Same here!  Having the "Hidden" attribute on ig:BoundDataField results in the error:

  "The Controls collection cannot be modified because the control contains code blocks (i.e.: <% ... %>)."

The problem is solved when you remove the Runat="server" from the html head tag.