Determining file extension given a FileStream

Question

Is there any way to know the type of the FileStream . I have a function that takes a FileStream object and I want to determine the file extension based on that FileStream .

Answer 1

If the stream is really a FileStream then you should be able to do the following

var ext = Path.GetExtension(fileStream.Name);

If it's a plain old Stream though then it's not generally possible to get the extension because a Stream can be created for any stream of bytes. It doesn't have to have a backing file.

Update

As Chris pointed out in the comments there is another SO question which is relevant to this discussion. It's discussing heuristics for determining type of a byte[] which can then be mapped to a probable original signature.

• In C#, how can I know the file type from a byte[]?

It's by no means foolproof but may be helpful to you.

Answer 2

 string extension = Path.GetExtension(myFileStream.Name);

Answer 3

Yes, using the file name the following will return .txt (including the . ):

var path = myFileStream.Name;
return Path.GetExtension(path);