MIME-Type for Excel XML (ASP.NET 3.5)

Question

I use CarlosAG-Dll which creates a XML-Excel-file for me (inside a MemoryStream).

Response.ContentType = "application/vnd.ms-excel";
Response.AppendHeader("content-disposition", "myfile.xml");
memory.WriteTo(Response.OutputStream);

My Problem here is, that I get at client side a myfile.xls (IE) or a myfile.xml.xls (FF) and therefore get an annoying security warning from excel.

I tried it as well with application/vnd.openxmlformats-officedocument.spreadsheetml.sheet (xlsx) but then it won't even open.

So I need to either cut the .xml and send it as vnd.ms-excel (how?) or take another MIME-type (but which one?).

edit: I found a bug description here

I wonder if this is still open and why?

Prasanth Prasanth · Accepted Answer · 2011-11-17T11:52:31

Use like this

Response.ContentType = "application/vnd.ms-excel";

Response.AppendHeader("content-disposition", "attachment; filename=myfile.xls");

For Excel 2007 and above the MIME type differs

Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

Response.AppendHeader("content-disposition", "attachment; filename=myfile.xlsx");

See list of MIME types

Office 2007 File Format MIME Types

EDIT:

If the content is not a native Excel file format, but is instead a text based format (such as CSV, TXT, XML), then the web site can add the following HTTP header to their GET response to tell IE to use an alternate name, and in the name you can set the extension to the right content type:
Response.AddHeader "Content-Disposition", "Attachment;Filename=myfile.csv"

For more details see this link

MIME-Type for Excel XML (ASP.NET 3.5)

3 Answers