Within a C# program, is there any way to tell if a file is a text file or not? I mean a real way, not just basing your conclusion on a file name extension.

It would be in the file header, its the first x bytes (I can't remember how many 'x' is - maybe 2).

Test by, creating a text file, read it into a byte array and check the first two bytes.

Then create another one and see if it matches the first two bytes. If so you've got your file signature.