The Controls collection cannot be modified because the contr

Question

i am using printclass in my appcode

from code behind printimgbtn click event i am calling static class method which had arguments as contorl and string

this is class code :

public static void PrintWebControl(Control ctrl, string Script)

    {

        //if (System.Web.HttpContext.Current.(string)Session["isgrid"] == "grid")

        //{

        //    GridView grid = (GridView)ctrl;

        //    grid.AllowPaging = false;

        //    grid.DataBind();

        //}

        StringWriter stringWrite = new StringWriter();

        System.Web.UI.HtmlTextWriter htmlWrite = new System.Web.UI.HtmlTextWriter(stringWrite);

        if (ctrl is WebControl)

        {

            Unit w = new Unit(100, UnitType.Percentage); ((WebControl)ctrl).Width = w;

        }

        Page pg = new Page();

        pg.EnableEventValidation = false;

        if (Script != string.Empty)

        {

            pg.ClientScript.RegisterStartupScript(pg.GetType(), "PrintJavaScript", Script);

        }

        HtmlForm frm = new HtmlForm();

        pg.Controls.Add(frm);

        frm.Attributes.Add("runat", "server");

        frm.Controls.Add(ctrl);

        pg.DesignerInitialize();

        pg.RenderControl(htmlWrite);

        string strHTML = stringWrite.ToString();

        HttpContext.Current.Response.Clear();

        HttpContext.Current.Response.Write(strHTML);

        HttpContext.Current.Response.Write("<script>window.print();</script>");

        HttpContext.Current.Response.End();

    }

code behind code : 

protected void btnPrint_Click(object sender, ImageClickEventArgs e)

{

    

    PrintHelper.PrintWebControl(PnlExportButtons0,string.Empty);

}

but it is showing the error  :

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