Yesterday’s post, “.NET 11 Preview - MIME Type Lookups”, looked at how to get the MIME type of a file given its extension using the new MediaTypeMap class.

In today’s post we look at the opposite problem - how to get the extension given the MIME type.

This is also addressed using the MediaTypeMap class, via the GetExtension method.

The code is as follows:

var extension = MediaTypeMap.GetExtension("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
Console.WriteLine(extension);

This will return the following:

.xlsx

In the event the MIME type is unknown, a null is returned.

mimeExtension

TLDR

The MediaTypeMap class has a GetExtension method that gets the extension of a given MIME type.

Happy hacking!