Question

How can I extend the Path.GetInvalidFileNameChars to include my own set of characters that is illegal in my application?

string invalid = new string(Path.GetInvalidFileNameChars()) + new string(Path.GetInvalidPathChars());

If I wanted to add the ‘&’ as an illegal character, could I do that?

Answer 1

You can’t modify an existing function, but you can write a wrapper function that returns Path.GetInvalidFileNameChars() and your illegal characters.

public static string GetInvalidFileNameChars() {
    return Path.GetInvalidFileNameChars().Concat(MY_INVALID_FILENAME_CHARS);
}