Convet Data into CSV file in Asp.Net

 Source Code

<table class="style1">

        <tr>

            <td>

                &nbsp;

            </td>

        </tr>

        <tr>

            <td>

                <asp:GridView ID="GridView1" runat="server">

                </asp:GridView>

            </td>

        </tr>

        <tr>

            <td>

                <asp:Button ID="BtnCSV" runat="server" Text="CSV" OnClick="BtnCSV_Click" />

            </td>

        </tr>

        <tr>

            <td>

                &nbsp;

            </td>

        </tr>

    </table>

C# Code

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

using System.IO;

public partial class FrmCSVfile : System.Web.UI.Page

{

    SqlConnection con;

    SqlDataAdapter da;

    DataTable dt;

    protected void Page_Load(object sender, EventArgs e)

    {

        if (IsPostBack == false)

        {

            con = new SqlConnection(ConfigurationManager.ConnectionStrings["DBConnection"].ConnectionString);

            da = new SqlDataAdapter("select * from demo", con);

            dt = new DataTable();

            da.Fill(dt);

            GridView1.DataSource = dt;

            GridView1.DataBind();

            ViewState["data"] = dt;

        }

    }

    protected void BtnCSV_Click(object sender, EventArgs e)

    {       

        CreateCSVFile(dt, @"C:\MasterBackup_satyajit\Satyajit Pradhan\xx.csv");

    }

    public void CreateCSVFile(DataTable dt, string strFilePath)

    {     

        dt = (DataTable)ViewState["data"]; 

        StreamWriter sw = new StreamWriter(strFilePath, false);

        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);

        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();

    }

}