private static string nth(int n)

nThNumber.cs

        /// <summary>
        /// Given a number (n) returns a string referring to that number (n)
        /// using (st), (nd), (th), (rd) as suffixes.
        /// </summary>
        /// <param name="n">The number to convert to nth notation.</param>
        /// <returns>The passed number in nth notation.</returns>
	private static string nth(int n)
	{
		switch (n) {
			case 11:
			case 12:
			case 13:
			case 14:
				return n + "th";
			default:
    			switch (n % 10) {
                      		case 1:
                                    	return n + "st";
                            	case 2:
                 	            	return n + "nd";
    	                	case 3:
        	                  	return n + "rd";
                	 	default:
                                	return n + "th";
			}
		}
	}

"teens" are a failing edge case here. (nth(11) => "11st" instead of "11th", and so on)

Here is Ruby's implementation of the ordinalize method.

Just these 4 needed to be patched up. Ty.
case 11:
case 12:
case 13:
case 14:
return n + "th";