How to check XML whitespace char

Working on XPointer parser for the XInclude.NET project I just realized there is no way (if I'm not mistaken) in .NET to check if a character is XML whitespace character. Plus all that functionality needed when parsing XML lexical constructs. No big deal, had to resort to old java trick:

public static bool IsWhitespace(char ch) {
    return (ch <= 0x0020) &&
        (((((1L << 0x0009) |
        (1L << 0x000A) |
        (1L << 0x000C) |
        (1L << 0x000D) |
        (1L << 0x0020)) >> ch) & 1L) != 0);
}

And that's a double pity, because XmlCharType class does implement all that XML-related lexical jazz in a very optimized way, but it's internal and not all of its power is exposed through other means (e.g. it's possible to verify a string as XML NCName using XmlConvert.VerifyNCName(string) method, which leverages XmlCharType underneath).