How to Toggle String Case in .NET

private const int AddressBitsPerUnit = 5;
private const int BitsPerElement = 32;
private const int BitIndexMask = BitsPerElement - 1;
private static readonly int[] ValidLatinChars = { 0, 0, 134217726, 134217726, 0, 0, 2139095039, 2139095039 };
public static string ToggleCase_SimmoTech_MacMaverick( string s )
{
  TextInfo currentCultureTextInfo = CultureInfo.CurrentCulture.TextInfo;
  char[] chs = s.ToCharArray();
  for ( int i = 0; i < s.Length; ++i )
  {
    char ch = chs[i];
    if ( ch <= 0xFF )
    {
      int bitSet = 1 << ( ch & BitIndexMask );
      if ( ( ValidLatinChars[( ch >> AddressBitsPerUnit )] & bitSet ) == bitSet )
      {
        chs[i] = (char) ( ch ^ 0x20 );
      }
      continue;
    }
    switch ( char.GetUnicodeCategory( ch ) )
    {
      case UnicodeCategory.UppercaseLetter:
        chs[i] = currentCultureTextInfo.ToLower( ch );
        break;
      case UnicodeCategory.LowercaseLetter:
        chs[i] = currentCultureTextInfo.ToUpper( ch );
        break;
    }
  }
  return ( new string( chs ) );
}