My application generates XLSX files based on a users requirements.
After the XLSX file is generated the user is redirected to where the file is saved using Response.Redirect…
Response.Redirect("filename.xlsx")
When the user then opens the file… they recieve this message.
The file you are trying to open, ‘filename.xls’, is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?
As a temporary fix I’ve instructed my users to press “Yes” when they receive this message and the file opens perfectly fine.
Does anyone have any ideas why IE6 is trying to open an XLSX file as an XLS?
Note: I have a similar application that generates PPTX files in the same manner – and these open without a problem.
I’ve found that it is an issue with older versions of windows server.
Both the xlsx MIME type needs to be added and there are also a couple driver updates that need to be installed (I don’t know specifically which ones. Our IT department is taking care of it)
To add the MIME type: Go to IIS Manager and add the .xlsx MIME type. (Documentation).
The MIME type that needs to be added is:
Further information on this can be found here: http://technet.microsoft.com/en-us/library/ee309278(office.12).aspx