Ordinal suffixes in English for the nth degree

Whether your ToString() method for a numeric type returns a suffix, as in the French 'ieme', or not, you still might be able to use this one for English, which returns suffixes for 1031^st, 23,589^th, 403^rd, and 352^nd correctly; and might well do so for any other numbers you can think of within the range of the UInt32.

public static string NUMthOF(UInt32 v)
{
  string thstndrd = "thstndrd", res=""; int k; UInt32 w;
  w = v; v = w % 100; res = w.ToString();
  if ((v < 21) & (v > 3)) k = 0;
  else k = (int)(v % 10); // Error was here, i.e., "% 100"
  if (k > 3) k = 0;
  res = res+thstndrd.Substring(k << 1, 2);
  return res;
}

If you're a web developer, you might prefer this one instead:

public static string NUMthOF(UInt32 v, bool forHTML)
{
  string thstndrd = "thstndrd", res=""; int k; UInt32 w;
  w = v; v = w % 100; res = w.ToString();
  if ((v < 21) & (v > 3)) k = 0;
  else k = (int)(v % 10); // Error was here, too.
  if (k > 3) k = 0;
  if (forHTML) res = res + "";
  res = res+thstndrd.Substring(k << 1, 2);
  if (forHTML) res = res + "";
  return res;
}

On a re-edit: Thanks to Luc Pattyn for pointing out the fact that 22 was returning "th" for a suffix. The modulus needs to be ten in the statements above where I'd inserted one hundred.