Export to CSV Website asp

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ASP.NET

CSV

I have a GridView and when I click Export Button to export my data into CSV. I click the button and it takes all the data correctly but it doesn't show anything, no popup to ask me to open or to save .

Here is my code

 protected void btnExport_Click(object sender, EventArgs e)
{
    ExportCSV();
}

protected void ExportCSV()
{
    GridViewSW.DataSource = ViewState["source"];
    Response.Clear();
    Response.Buffer = true;
    Response.AddHeader("content-disposition", "attachment;filename=Orders.csv");
    Response.Charset = "";
    Response.ContentType = "application/text";
    GridViewSW.AllowPaging = false;        
    GridViewSW.DataBind();

    StringBuilder columnbind = new StringBuilder();
    for (int k = 0; k < GridViewSW.Columns.Count; k++)
    {
        columnbind.Append(GridViewSW.Columns[k].HeaderText + ",");
    }
    columnbind.Append("\r\n");

    for (int i = 0; i < GridViewSW.Rows.Count; i++)
    {
        for (int j = 0; j < GridViewSW.Columns.Count; j++)
        {
            columnbind.Append(GridViewSW.Rows[i].Cells[j].Text + ",");
        }
        columnbind.Append("\r\n");
    }



    Response.Output.Write(columnbind.ToString());
    Response.Flush();
    Response.End();

}