Ordinal suffixes in English for the nth degree

What about

public static string NUMthOF(UInt32 v)
{
    return v.ToString() + 
        // Append the ordinal suffix for the unit digit
        // unless the ten digit is a one (force 'th')
        "thstndrdthththththth".Substring(2 * (int)(v / 10 % 10 != 1 ? v % 10 : 0), 2);
}

?

Now all the crypticism is concentrated in a single expression :)