Corrupted data

[GoogleCodeExporter]

What steps will reproduce the problem?

We are exporting file like this:

 [HttpPost]
        public ActionResult ExportFile(string EntryFile)
        {
            var list = JsonConvert.DeserializeObject<Entry>(EntryFile);

            return new FileContentResult(Export(list.CompositionEntry),
                    "application/vnd.ms-excel") { FileDownloadName = "fix_list.xls" };
        }

Everything seem to work, but Excel reports the problem: 
Damage to the file was so extensive that repairs were not possible. Excel 
attempted to recover your formulas and values, but some data may have been lost 
or corrupted.
When I click Ok, data is exported correctly, but we still don`t want error to 
be shown. Any ideas??? 

Original issue reported on code.google.com by [email protected] on 30 Jan 2014 at 3:15