Cannot export to Excel in IE 11 - asp.net

Question

I have a web application that exports data from a gridview to Excel. It works fine in Chrome but doesn't work in IE 11 and Firefox. I see a lot of issues with this when I google it but this error seems to be unique.
protected void ExportToExcel(List<MapAmericas.Model.Project> Projects)
{
Response.Clear();
Response.Buffer = true;
Response.ContentType = "application/vnd.ms-excel";
Response.ContentEncoding = System.Text.Encoding.Unicode;
Response.AddHeader("content-disposition", "attachment;filename=MyFile" + DateTime.Now.ToString() + ".xls");
Response.Charset = "";
Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble());
this.EnableViewState = false;
System.IO.StringWriter sw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htw = new System.Web.UI.HtmlTextWriter(sw);
GridView gv = new GridView();
gv.AutoGenerateColumns = false;
gv.RowDataBound += new GridViewRowEventHandler(dataExportExcel_ItemDataBound);
gv.DataSource = Projects;
gv.DataBind();
gv.RenderControl(htw);
Response.Write(AddExcelStyling()); //this contains the opening html elements
StringBuilder sbResponseString = new StringBuilder();
sbResponseString.Append(sw + "</body></html>");
Response.Write(sbResponseString.ToString());
Response.Flush();
Response.Close();
Response.End();
}
...and the issue I'm getting has to do with not being able to access Temporary Internet Files. I get a popup "Problems during Load" and about a dozen entries: "Missing File...Temporary Internet Files\Content\" and then I get a message reading "Unable to read file".
I had an image to represent the error but I'm not able to upload images.
When I click on one of the links, it loads up my webpage without any styles and I don't get an excel file.
Does anyone know what the issue would be?

Answer 1

I got it! I added 2 lines of code to my existing code and it works. See lines marked with **:
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.Buffer = true;
//HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
HttpContext.Current.Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Unicode;
HttpContext.Current.Response.AddHeader("content-disposition", "attachment;filename=Panorama_Project-" + DateTime.Now.ToString() + ".xls");
HttpContext.Current.Response.Charset = "";
HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble());
this.EnableViewState = false;
System.IO.StringWriter sw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htw = new System.Web.UI.HtmlTextWriter(sw);
GridView gv = new GridView();
gv.AutoGenerateColumns = false;
gv.RowDataBound += new GridViewRowEventHandler(dataExportExcel_ItemDataBound);
gv.DataSource = Projects;
gv.DataBind();
gv.RenderControl(htw);
HttpContext.Current.Response.Write(AddExcelStyling());
StringBuilder sbResponseString = new StringBuilder();
sbResponseString.Append(sw + "</body></html>");
**HttpContext.Current.Response.AddHeader("Content-Length", sbResponseString.Length.ToString());**
HttpContext.Current.Response.Write(sbResponseString.ToString());
//HttpContext.Current.Response.Flush();
//HttpContext.Current.Response.Close();
//HttpContext.Current.Response.End();
**System.Web.HttpContext.Current.ApplicationInstance.CompleteRequest();**
It seems as though it was trying to display the entire Response object which included my page and all linked resources. The Content-Length and replacing Reponse.End and Response.Flush with System.Web.HttpContext.Current.ApplicationInstance.CompleteRequest() seems to do the trick.

Answer 2

This is the simplified version of an Export To Excel function (for a datatable) that I use and one that works for all the browsers. See if this helps. The code is quite similar to yours though:
public void ExportDataToExcel(String FileName, DataTable dtData)
{
// get gridview out of datatable
GridView gv = new GridView();
gv.AllowPaging = false;
gv.DataSource = dtData;
gv.DataBind();
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.Buffer = true;
HttpContext.Current.Response.AddHeader("content-disposition",
"attachment;filename=" + FileName + ".xls");
HttpContext.Current.Response.Charset = "";
HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
for (int i = 0; i < gv.Rows.Count; i++)
{
// Apply text style to each Row
gv.Rows[i].Attributes.Add("class", "textmode");
}
gv.RenderControl(hw);
HttpContext.Current.Response.Output.Write(sw.ToString());
// commenting this out to resolve this error
// System.Web.HttpException: The remote host closed the connection.
// The error code is 0x800703E3.
// HttpContext.Current.Response.Flush();
HttpContext.Current.Response.End();
}