How to convert series of integers into ordinals in C#

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C#7.0

we have 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 19th.

NOW: here is my question and exact want (Can i be able to change the highest value to be 1st and the next largest value will be 2nd, 3rd and 4th continuously within this series wherever we have similar integers we will have similar position say 19th and 19th will have 1st, 1st because they are both the largest values. but the positioning will continue as 3rd for 18th; 4th for 17th ; 5th for 16th; 6th for 15th; 7th for 14th; 8th for 13th; 9th for 12th; 10th for 11th; 11th for 10th; and 12th for 10th; 13th for 8th; etc.


is just like having 13 student in a class who took an examination and had different scores in a subject like English, when we want to rank them or say give them their result we need to calculate their position in the subject examination in such a way that we will definitely end up having some one in the class with the last position 13th even when we have student with similar position. this is what i want my button1_click event to do

thank you sir (for your help) and more help


can i be thought how to do it right please (thanks in advance) (am using c# in wpf)

What I have tried:

when my button convert is clicked with code:

private void btnconvert_Click(object sender, RoutedEventArgs e)
{
foreach (int num in txtresults.ToString())
{
string[] parts = txtresults.Text.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
double[] numbers = parts.Select(p => double.Parse(p)).ToArray();
double maximum = numbers.Max();
int position = Array.IndexOf(numbers, maximum);
parts[position] = AddOrdinal(num);
txtresults.Text = string.Join(" ", parts);
}
}

this is my method of conversion

public static string AddOrdinal(int num)
{
if (num <= 0) return num.ToString();

     switch (num % 100)
     {
         case 11:
         case 12:
         case 13:
             return num + "th";
     }
     switch (num % 10)
     {
         case 1:
             return num + "st";
         case 2:
             return num + "nd";
         case 3:
             return num + "rd";
         default:
             return num + "th";
     }
 }