The Controls collection cannot be modified because the contr

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("");

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. <% ... %>)