Export Gridview Data in Excel

  public void export_attendence()
    {
        string attachment = "attachment; filename=Student_attendence_Report.xls";
        Response.ClearContent();
        Response.AddHeader("content-disposition", attachment);
        Response.ContentType = "application/ms-excel";
        StringWriter sw = new StringWriter();
        HtmlTextWriter htw = new HtmlTextWriter(sw);
        GridView1.RenderControl(htw);
        Response.Write(sw.ToString());
        Response.End();

    }

public override void VerifyRenderingInServerForm(Control control)
    {
        /* Confirms that an HtmlForm control is rendered for the specified ASP.NET
           server control at run time. */
    }


<%@ Page Title="" Language="C#" MasterPageFile="~/vShksha.master" AutoEventWireup="true" CodeFile="expense_details.aspx.cs" Inherits="expense_details" EnableEventValidation="false"  %>