Problems exporting gridView to Excel

Problems exporting gridView to Excel

I am trying to export a GridView to Excel.
I have tried to follow steps found here:
http://www.programming-free.com/2012/09/aspnet-export-grid-view-to-excel.html#.UhUREpK1F9o
export gridview to excel file
And other similar sites.
My GridView does not have any special properties different from default
and my SqlDataSource uses filterExpression if that is important.
When I try the above mentioned solutions no exception occurs, but the
excel is not produced.
UPDATE
I forgot to mention that the GirdView is inside a asp:Content control. I
heard this might matter.
My code-behind goes something like this ( I have tried multiple things ).
Response.Clear();
Response.AddHeader("content-disposition",
"attachment;filename=FileName.xls");
Response.Charset = String.Empty;
EnableViewState = false;
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.ContentType = "application/vnd.xls";
System.IO.StringWriter stringWrite = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htmlWrite =
new HtmlTextWriter(stringWrite);
GridView3.RenderControl(htmlWrite);
Response.Write(stringWrite.ToString());
HttpContext.Current.ApplicationInstance.CompleteRequest();