C# - Make Exported .XLS File Editable?

How to make exported .XLS file Editable Thid code makes .XLS File Read Only

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using System;
using System.Data;
using System.Configuration;
using System.IO;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public class GridViewExportUtil
{
/// <param name="fileName"></param>
/// <param name="gv"></param>
public static void Export(string fileName, GridView gv)
{
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.AddHeader(
"content-disposition", string.Format("content-disposition", "attachment; filename={0}", fileName));
HttpContext.Current.Response.ContentType = "application/ms-excel";
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
HttpContext.Current.Response.Charset = System.Text.Encoding.Unicode.EncodingName;
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Unicode;
HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble());
using (StringWriter sw = new StringWriter())
{
using (HtmlTextWriter htw = new HtmlTextWriter(sw))
{
// Create a form to contain the grid
Table table = new Table();
// add the header row to the table
if (gv.HeaderRow != null)
{
GridViewExportUtil.PrepareControlForExport(gv.HeaderRow);
table.Rows.Add(gv.HeaderRow);
}
// add each of the data rows to the table
foreach (GridViewRow row in gv.Rows)
{
GridViewExportUtil.PrepareControlForExport(row);
table.Rows.Add(row);
}
// add the footer row to the table
if (gv.FooterRow != null)
{
GridViewExportUtil.PrepareControlForExport(gv.FooterRow);
table.Rows.Add(gv.FooterRow);
}
// render the table into the htmlwriter
table.RenderControl(htw);
// render the htmlwriter into the response
HttpContext.Current.Response.Write(sw.ToString());
HttpContext.Current.Response.End();
}
}
}
/// <summary>
/// Replace any of the contained controls with literals
/// </summary>
/// <param name="control"></param>
private static void PrepareControlForExport(Control control)
{
for (int i = 0; i < control.Controls.Count; i++)
{
Control current = control.Controls[i];
if (current is LinkButton)
{
control.Controls.Remove(current);
control.Controls.AddAt(i, new LiteralControl((current as LinkButton).Text));
}
else if (current is ImageButton)
{
control.Controls.Remove(current);
control.Controls.AddAt(i, new LiteralControl((current as ImageButton).AlternateText));
}
else if (current is HyperLink)
{
control.Controls.Remove(current);
control.Controls.AddAt(i, new LiteralControl((current as HyperLink).Text));
}
else if (current is DropDownList)
{
control.Controls.Remove(current);
control.Controls.AddAt(i, new LiteralControl((current as DropDownList).SelectedItem.Text));
}
else if (current is CheckBox)
{
control.Controls.Remove(current);
control.Controls.AddAt(i, new LiteralControl((current as CheckBox).Checked ? "True" : "False"));
}
if (current.HasControls())
{
GridViewExportUtil.PrepareControlForExport(current);
}
}
}
}