C#: Alternate the case of each letter in a given string and the first letter of the said string must be uppercase

Last update on August 25 2025 12:50:13 (UTC/GMT +8 hours)

Write a C# Sharp program to alternate the case of each letter in a given string. The first letter of this string must be uppercase.

Sample Solution:-

C# Sharp Code:

using System;
using System.Linq;

namespace exercises
{
    class Program
    {
        static void Main(string[] args)
        {
            // Declare and initialize a string variable
            string str1 = "c# Exercises";

            // Display the original string
            Console.WriteLine("Original string: " + str1);

            // Display the string after alternating the case of each letter
            Console.WriteLine("\nAfter alternating the case of each letter of the said string:\n" + test(str1));

            // Change the value of str1
            str1 = "C# is used to develop web apps, desktop apps, mobile apps, games and much more.";

            // Display the new original string
            Console.WriteLine("\nOriginal string: " + str1);

            // Display the string after alternating the case of each letter
            Console.WriteLine("\nAfter alternating the case of each letter of the said string:\n" + test(str1));
        }

        // Define a method 'test' that takes a string argument 'str' and returns a modified string with alternating case letters
        public static string test(string str)
        {
            // Double the spaces in the text
            string text = str.Replace(" ", "  ");
            string result_str = "";

            // Capitalize the first character of the string
            result_str += Char.ToUpper(str[0]);

            // Loop through each character in the text, starting from the second character
            for (int i = 1; i < text.Length; i++)
            {
                // Check if the index is even (alternating position)
                if (i % 2 == 0)
                    result_str += Char.ToUpper(text[i]); // Convert to uppercase and add to the result string
                else if (i % 2 != 0 && Char.IsUpper(text[i]))
                    result_str += Char.ToLower(text[i]); // Convert to lowercase and add to the result string if the character is already uppercase
                else
                    result_str += text[i]; // Add the character as it is to the result string
            }

            // Replace double spaces with single spaces in the result string
            result_str = result_str.Replace("  ", " ");

            // Return the modified string with alternating case letters
            return result_str;
        }
    }
}

Sample Output:

Original string: c# Exercises

After alternating the case of each letter of the said string:
C# ExErCiSeS

Original string: C# is used to develop web apps, desktop apps, mobile apps, games and much more.

After alternating the case of each letter of the said string:
C# Is UsEd To DeVeLoP wEb ApPs, dEsKtOp ApPs, mObIlE aPpS, GaMeS aNd MuCh MoRe.

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