Convert String From LowerCase To UpperCase Without Inbuilt Function

Introduction: Converting string from lowercase to uppercase without using any inbuilt function, in C#.

 

Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LowerTOUpper
{
    class LowerTOUpper
    {
       public static String ConvertToUpperCase(String input)
      {
         String output = "";
         for (int i = 0; i < input.Length; i++)
         {
            if (input[i] >= 'a' && input[i] <= 'z')
            {
               output += (char)(input[i] - 'a' + 'A');
            }
            else
               output += input[i];
         }
         return output;
      }

      static void Main(string[] args)
      {
         System.Console.Write("Enter a string: ");
         String input = System.Console.ReadLine();
         input = ConvertToUpperCase(input);
         System.Console.WriteLine("Converted String in Upper Case: " + input);
         Console.ReadLine();
      }
    }
}

Output