Question

I have this code which export data from GridView to csv. It works with other sites but not on this current one I’ve been developing.

The GridView is binded with DataTable in code behind. Following is the event that binds the fetch and bind the data to GridView.

    private void bindGridView()
    {
        //Fetching data from DB goes here

        myTable.Columns.Add("type", typeof(int));
        myTable.Columns.Add("rate", typeof(int));

        foreach (DataRow rows in myTable.Rows)
        {
            if (rows["dst"].ToString() == "1875")
            {
                rows["type"] = 1;
                rows["rate"] = 500;
                rows.AcceptChanges();
            }
            else if (rows["dst"].ToString() == "1876")
            {
                rows["type"] = 0;
                rows["rate"] = 30;
                rows.AcceptChanges();
            }
        }

        gridViewData.DataSource = myTable;
        gridViewData.AllowPaging = true;
        gridViewData.PageSize = 10;
        gridViewData.DataBind();
    }

Following is the button click event to export data from GridView

    protected void btnExportCDR_Click(object sender, EventArgs e)
    {
        if (gridViewData.Rows.Count == 0)
        {
            lblStatus.Text = "Data is empty. Can not export CDR. Please check your filtering dates.";
        }
        else
        {
            Response.Clear();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment;filename=CDRMMCC_" + System.DateTime.Now.ToShortDateString() + ".csv");
            Response.Charset = "";
            Response.ContentType = "application/text";


            bindGridView();
            gridViewData.AllowPaging = false;



            StringBuilder sb = new StringBuilder();

            //I did a trace here, gridViewData.Columns.Count is 0. That's why it got skipped, I think.
            for (int k = 0; k < gridViewData.Columns.Count; k++)
            {
                sb.Append(gridViewData.Columns[k].HeaderText + ",");

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

                }
                sb.Append("\r\n");
            }
            Response.Output.Write(sb.ToString());
            Response.Flush();
            Response.End();
        }
    }

Please advice.

Answer 1

If you use the AutoGenerateColumns property of the GridView set to true the Columns collection will be empty. The MSDN documentation for this property says:

“Automatically generated bound column fields are not added to the Columns collection”.

This is the reason your Columns collection is empty. As Henk Holterman pointed out use your DataTable directly to generate your CSV file.

An alternative approach would be to set the AutoGenerateColumns property to false and define the Columns explicitly.