Remove invalid (disallowed, bad) characters from FileName (or Directory, Folder, File) using C# .NET

Question

Hi, I've wrote this little method to achieve the goal in the subj., however, is there more efficient (simpler) way of doing this? I hope this can help somebody who will search for this like I did.

var fileName = new System.Text.StringBuilder();
fileName.Append("*Bad/\ :, Filename,? ");
// get rid of invalid chars
while (fileName.ToString().IndexOfAny(System.IO.Path.GetInvalidFileNameChars()) > -1)
{
    fileName = fileName.Remove(fileName.ToString().IndexOfAny(System.IO.Path.GetInvalidFileNameChars()), 1);
}

?

Answer 1

Try the following

public string MakeValidFileName(string name) {
  var builder = new StringBuilder();
  var invalid = System.IO.Path.GetInvalidFileNameChars();
  foreach ( var cur in name ) {
    if ( !invalid.Contains(cur) ) {
      builder.Append(cur);
    }
  }
  return builder.ToString();
}

Answer 2

If you look for "concise" when you say simple:

public string StripInvalidChars(string filename) {
  return new String(
    filename.Except(System.IO.Path.GetInvalidFileNameChars()).ToArray()
  );
}

That said, I'd go with JaredPar's solution. It's probably easier to read (depending on taste, background), my gut feeling is that it is more efficient (although I'm not sure how efficient you have to be stripping that dozen of invalid chars from a limited length filename) and his use of a StringBuilder() seems to fit perfectly to your example.