Cleans filenames, source: http://stackoverflow.com/questions/309485/c-sharp-sanitize-file-name/847251#847251

gistfile1.cs

public static string MakeValidFileName( string name )
{
   string invalidChars = Regex.Escape( new string( Path.GetInvalidFileNameChars() ) );
   string invalidReStr = string.Format( @"[{0}]+", invalidChars );
   return Regex.Replace( name, invalidReStr, "_" );
}