using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class ExportGridView : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            GridView1.DataSource = BindData();
            GridView1.DataBind();
        }
    }

    

    private string ConnectionString
    {

        get { return @"Server=localhost;Database=Northwind;
        Trusted_Connection=true"; }

    }

    

    private DataSet BindData()
    {
        // make the query
        string query = "SELECT * FROM Categories";
        SqlConnection myConnection = new SqlConnection(ConnectionString);
        SqlDataAdapter ad = new SqlDataAdapter(query, myConnection);
        DataSet ds = new DataSet();
        ad.Fill(ds, "Categories");
        return ds;

    }




    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Clear();

        Response.AddHeader("content-disposition", "attachment;
        filename=FileName.xls");

        Response.Charset = "";

        // If you want the option to open the Excel file without saving than

        // comment out the line below

        // Response.Cache.SetCacheability(HttpCacheability.NoCache);

        Response.ContentType = "application/vnd.xls";

        System.IO.StringWriter stringWrite = new System.IO.StringWriter();

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

        GridView1.RenderControl(htmlWrite);

        Response.Write(stringWrite.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.

    }
}