New Post: "unreadable content" error when opening Excel file created via ClosedXML

I was getting a very similar error when downloading Excel files from an ASP.NET site.  Turns out I also needed the Content-Length header.  Here's a code snippet:   MemoryStream stream = export.ExportEx(types, ids); Response.Clear(); Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"; Response.AddHeader("content-disposition", "attachment;filename=\"AnalysisExport.xlsx\""); Response.AddHeader("Content-Length", stream.Length.ToString()); stream.WriteTo(Response.OutputStream); stream.Close();