How to reverse a string without using array and for loop

using System;
using System.Text;

class Program
{
    static void Main()
    {
        string str = "Hello, World!";
        string reversedStr = ReverseString(str);
        Console.WriteLine(reversedStr);
    }

    static string ReverseString(string str)
    {
        if (str.Length <= 1)
            return str;

        return ReverseString(str.Substring(1)) + str[0];
    }
}

using System;
using System.Text;

class Program
{
    static void Main()
    {
        string input = "Hello, World!";
        string reversed = ReverseString(input);
        Console.WriteLine(reversed);
    }

    static string ReverseString(string input)
    {
        if (input.Length <= 1)
            return input;

        StringBuilder sb = new StringBuilder();
        sb.Append(input[input.Length - 1]);
        sb.Append(ReverseString(input.Substring(0, input.Length - 1)));
        return sb.ToString();
    }
}
 

using System;
using System.Text;

class Program
{
    static void Main()
    {
        string originalString = "Hello, World!";
        string reversedString = ReverseString(originalString);
        Console.WriteLine(reversedString);
    }

    static string ReverseString(string input)
    {
        if (input.Length <= 1)
            return input;
        return ReverseString(input.Substring(1)) + input[0];
    }
}

using LINQ:

string.Concat(yourStringVariableHere.Reverse());

note that LINQ uses loops internally. You can't easily reverse a string without using loops at all