how to Export data into Text/CSV file from grid view in asp.net using c#

To export the GridView as CSV, I am running a two for loops. While looping through the GridView columns and appending comma after each column and while looping through rows appending new line character. Refer the code below.

protected void btnExportCSV_Click(object sender, EventArgs e)
{
    Response.Clear();
    Response.Buffer = true;
    Response.AddHeader("content-disposition",
     "attachment;filename=GridViewExport.csv");
    Response.Charset = "";
    Response.ContentType = "application/text";
 
    GridView1.AllowPaging = false;
    GridView1.DataBind();
 
    StringBuilder sb = new StringBuilder();
    for (int k = 0; k < GridView1.Columns.Count; k++)
    {
        //add separator
        sb.Append(GridView1.Columns[k].HeaderText + ',');
    }
    //append new line
    sb.Append("\r\n");
    for (int i = 0; i < GridView1.Rows.Count; i++)
    {
        for (int k = 0; k < GridView1.Columns.Count; k++)
        {
            //add separator
            sb.Append(GridView1.Rows[i].Cells[k].Text + ',');
        }
        //append new line
        sb.Append("\r\n");
    }
    Response.Output.Write(sb.ToString());
    Response.Flush();
    Response.End();
}

To avoid the error you will need to add this event which ensures that the GridView is Rendered before exporting.

public override void VerifyRenderingInServerForm(Control control)
{
    /* Verifies that the control is rendered */
}