export to excel multi gridview in asp.net

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<%@ Page Language="C#" MasterPageFile="~/Masters/Admin.master" EnableEventValidation="false" AutoEventWireup="true"
    CodeFile="AccountDetails.aspx.cs" Inherits="User_Account_Details" Title="Account Details :: Saagi Trade Mart Pvt. Ltd. " %>


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protected void btnExportFromDatagrid_Click(object sender, EventArgs e)
    {
        ExportGridToExcel(GridView1, "StudentMarks.xls");
       // Exportexcels();

    }

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public void ExportGridToExcel(GridView grdGridView, string fileName)
    {
        Response.Clear();
        Response.AddHeader("content-disposition",
            string.Format("attachment;filename={0}.xls", fileName));
        Response.Charset = "";
        Response.ContentType = "application/vnd.xls";

        StringWriter stringWrite = new StringWriter();
        HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
        grdGridView.AllowPaging = false;
        grdGridView.DataBind();
        grdGridView.RenderControl(htmlWrite);
       
        Response.Write(stringWrite.ToString());
        Response.End();
    }



 public override void VerifyRenderingInServerForm(Control control)
    {
       
       
    }



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CODE FOR EXPORT MULTI GRIDVIEW TO EXCELL SHEET
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 protected void Button2_Click(object sender, EventArgs e)
    {
        ExportGridToExcel(GridView1, GridView2,"WorkingIncome.xls", "NonWorkingIncome.xls");

    }
    public void ExportGridToExcel(GridView grdWorking, GridView grdNonworking, string working, string nonworking)
    {
        ArgumentOutOfRangeException arg = new ArgumentOutOfRangeException();
       
        Response.Clear();
        Response.AddHeader("content-disposition", string.Format("attachment;filename={0}.xls", working, nonworking));
     

        Response.Charset = "";
        Response.ContentType = "application/Wrk.xls";
        Response.ContentType = "application/NWrk.xls";

        StringWriter stringWriteW = new StringWriter();
        HtmlTextWriter htmlWriteW = new HtmlTextWriter(stringWriteW);
        StringWriter stringWriteNon = new StringWriter();
        HtmlTextWriter htmlWriteNon = new HtmlTextWriter(stringWriteNon);


        grdWorking.AllowPaging = false;
        grdWorking.DataBind();
        grdWorking.RenderControl(htmlWriteW);


        grdNonworking.AllowPaging = false;
        grdNonworking.DataBind();
        grdNonworking.RenderControl(htmlWriteNon);


        Response.Write(stringWriteW.ToString());
        Response.Write(stringWriteNon.ToString());
         Response.End();
    }



    public override void VerifyRenderingInServerForm(Control control)
    {


    }
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when panel printing
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---------On (Print.aspx) -----------------
protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["AdminID"] == null)
        {
            Response.Redirect("~/KBCLogin.aspx");
        }
        Control ctrl = (Control)Session["ctrl"];
        PrintHelper.PrintWebControl(ctrl);
    }

------------On Print button (Panel Printing)-----------------

 protected void btn_Print_Click(object sender, EventArgs e)
    {
        panel1.Visible = true;
        Session["ctrl"] = panel1;
        ClientScript.RegisterStartupScript(this.GetType(), "onclick", "<script language=javascript>window.open('Print.aspx','PrintMe','height=430px,width=390px,scrollbars=1');</script>");

    }