System.Threading.ThreadAbortException occurred in mscorlib.dll occuring persitently

Im new to .net, Im using the following code to transfer from gridview to excel:

         protected void toexcelbutton_Click(object sender, EventArgs e)
        {
       Response.ClearContent();
    Response.Buffer = true;
    Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "attendancedatereport.xls"));
    Response.ContentType = "application/ms-excel";
    StringWriter sw = new StringWriter();
    HtmlTextWriter htw = new HtmlTextWriter(sw);
    GridView1.AllowPaging = false;
    GridView1.AllowSorting = false;
    GridView1.DataBind();
    HtmlForm htmfrm = new HtmlForm();
    GridView1.Parent.Controls.Add(htmfrm);
    htmfrm.Attributes["runat"] = "server";
    htmfrm.Controls.Add(GridView1);
    htmfrm.RenderControl(htw);
    Response.Write(sw.ToString());

    HttpContext.Current.ApplicationInstance.CompleteRequest();
}

When i run this code,i get an exception:

A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll.

But,when i run the same code in another page for another gridview,it works perfectly.,i tried,adding

EnableEventValidation="false"

to the aspx page, and

<pre lang="cs">public override void VerifyRenderingInServerForm(Control control)
{
   /* Verifies that the control is rendered */
}</pre>

to the aspx.cs page,

i tried clearing the temporary files, still i get the same error,for more than 5hours i have tried,nothing is working.

I then tried select the Debug -> Exceptions menu item, and in the dialog that appears, checked the first checkbox for "Common Language Runtime Exceptions,

i get this error:

Access to the path 'C:\Users\abcd\AppData\Local\Temp\Temporary ASP.NET Files\mark\3f229106\f785abea\App_Web_0h5ppn4m.dll' is denied.