using System;

public class Program

{

    // Return the int's ordinal extension.

    //public static string ToOrdinal(this int value)

    public static string ToOrdinal(object data)

    {

        Int64 value = 0;

        // Start with the most common extension.

        string extension = "th";

        try

        {

            value = Convert.ToInt64(data);

​

            // Examine the last 2 digits.

            Int64 last_digits = value % 100;

​

            // If the last digits are 11, 12, or 13, use th. Otherwise:

            if (last_digits < 11 || last_digits > 13)

            {

                // Check the last digit.

                switch (last_digits % 10)

                {

                    case 1:

                        extension = "st";

                        break;

                    case 2:

                        extension = "nd";

                        break;

                    case 3:

                        extension = "rd";

                        break;

                }

            }

            extension = data + extension;

        }

        catch (Exception ex)

        {

            extension = data.ToString();

        }

        return extension;

    }

    public static void Main()

    {

        Console.WriteLine(ToOrdinal("49ff").ToString());

    }

}