How to Toggle String Case in .NET

Several of the answers here lack fallbacks for Unicode.

static string ToggleCaseHA(string str) {
    char[] chs = str.ToCharArray();
    for (int i = chs.Length - 1; i >= 0; i--) {
        char ch = chs[i];
        char foo = (char)(ch & ~0x20);
        if ((foo >= 0x41 && foo <= 0x5a) || (foo >= 0xc0 && foo <= 0xde && foo != 0xd7))
            chs[i] = (char)(ch ^ 0x20);
        else if (foo == 0xdf || (ch > 0xff && char.IsLetter(ch))
            chs[i] = char.IsLower(ch) ? char.ToUpper(ch) : char.ToLower(ch);
    }
    return new string(chs);
}

Note by Alex Bell: this algorithm was included in test set at: http://webinfocentral.com/resources/toggleCaseAlgorithm.aspx[^] . This algorithm indeed can process the Unicode String, but so can do all other algorithms (Alternate 1, Alternate 2, etc.) except for the "TogglebyCeChode" (which is the fastest, but does not work on Unicode text). After sample testing, this proposed algorithm demonstrated just a marginal performance increase over Alternate 1 and Alternate 2.