protected void Button1_Click(object sender, EventArgs e)

    {

        string strConn = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();

        SqlConnection conn = new SqlConnection(strConn);

        SqlDataAdapter da = new SqlDataAdapter("select * from employees", conn);

        DataSet ds = new DataSet();

        da.Fill(ds, "Emp");

        GridView1.DataSource = ds.Tables["Emp"].DefaultView;

        GridView1.DataBind();

        DataTable dt = ds.Tables["Emp"];

        CreateCSVFile(dt, "c:\\csvData.csv");

    }

    public void CreateCSVFile(DataTable dt, string strFilePath)

    {

        #region Export Grid to CSV

        // Create the CSV file to which grid data will be exported.

        StreamWriter sw = new StreamWriter(strFilePath, false);

        // First we will write the headers.

        //DataTable dt = m_dsProducts.Tables[0];

        int iColCount = dt.Columns.Count;

        for (int i = 0; i < iColCount; i++)

        {

            sw.Write(dt.Columns[i]);

            if (i < iColCount - 1)

            {

                sw.Write(",");

            }

        }

        sw.Write(sw.NewLine);

        // Now write all the rows.

        foreach (DataRow dr in dt.Rows)

        {

            for (int i = 0; i < iColCount; i++)

            {

                if (!Convert.IsDBNull(dr[i]))

                {

                    sw.Write(dr[i].ToString());

                }

                if (i < iColCount - 1)

                {

                    sw.Write(",");

                }

            }

            sw.Write(sw.NewLine);

        }

        sw.Close();

        #endregion

    }