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?
Best Answer
Use like this
For Excel 2007 and above the MIME type differs
See list of MIME types
Office 2007 File Format MIME Types
EDIT:
For more details see this link