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Removing bad chars from a string

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Remove illegal chars from a string using regular expressions

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  1. /// <summary>
  2.     /// Removes "unsafe" characters from the string.
  3.     /// </summary>
  4.     /// <param name="unsafeString">String to edit</param>
  5.     /// <returns>A "safe" string</returns>
  6.     public static string GetSafeString(string unsafeString)
  7.     {
  8.       // Grab the system invalid chars 
  9.       // Then remove the chars in our IgnoreInvalidChars collection
  10.       char[] systemInvalidChars = Path.GetInvalidFileNameChars();
  11.       List<char> unacceptableChars = new List<char>();
  12.       unacceptableChars.AddRange(systemInvalidChars);
  13.  
  14.       List<char> okayChars = new List<char>();
  15.       okayChars.AddRange(IgnoreInvalidChars);
  16.  
  17.       // Remove the items in unaccpetableChars
  18.       // that make okayChars.Contains(char) return true
  19.       unacceptableChars.RemoveAll(okayChars.Contains);
  20.  
  21.       List<char> needEscapeChars = new List<char>();
  22.       needEscapeChars.AddRange(NeedEscapeInRegexChars);
  23.  
  24.       string regexPattern = StartingRegexPattern;
  25.  
  26.       // Write each char into a string
  27.       // some chars need to be further escaped
  28.       // for regex to handle them.
  29.       for (int i = 0; i < unacceptableChars.Count; i++)
  30.       {
  31.         //If the char needs to have the escape char in front of it
  32.         // add the escape char
  33.         if (needEscapeChars.Contains(unacceptableChars[i]))
  34.         {
  35.           regexPattern = regexPattern + RegexEscapeString;
  36.         }
  37.         regexPattern = regexPattern + unacceptableChars[i];
  38.       }
  39.  
  40.       regexPattern = regexPattern + ClosingRegexPattern;
  41.  
  42.       return Regex.Replace(unsafeString.Trim(), regexPattern, string.Empty);
  43.     }
  44.  
  45.  
  46. private static readonly string StartingRegexPattern = "[";
  47.     private static readonly string ClosingRegexPattern = "]";
  48.     private static readonly string RegexEscapeString = @"\";
  49.  
  50.     private static readonly char[] IgnoreInvalidChars = 
  51.       { '\n', '\r', '\a', '\b', '\t', '\0', '\v', '\f' };
  52.  
  53.     private static readonly char[] NeedEscapeInRegexChars = 
  54.       { '\\', '/' };

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