How do you check a file type when there is no extension in c#

Question

How do you check a file type when there is no extension in c#

For instance, I have files with no extension, that are either .mp4 or .flv format (just no extension).

Answer 1

I've heard of reading the first few bytes of a file's contents and making an educated guess at the file's format. This link seems promising:

Using .NET, how can you find the mime type of a file based on the file signature not the extension