Regular expressions in C# for file name validation

Question

What is a good regular expression that can validate a text string to make sure it is a valid Windows filename? (AKA not have \\/:*?\"<>| characters).

Answer 1

As answered already, GetInvalidFileNameChars should do it for you, and you don't even need the overhead of regular expressions:

if (proposedFilename.IndexOfAny(System.IO.Path.GetInvalidFileNameChars()) != -1)
{
  MessageBox.Show("The filename is invalid");
  return;
}