string manipulation and sb

using System;
using System.Text;
class StringManipulation
{
    static void Main()
    {
        string s = "Hello";
        Console.WriteLine("Original String: " + s);
        s = s.ToUpper();
        Console.WriteLine("Uppercase: " + s);
        s = s.Replace("HELLO", "WORLD");
        Console.WriteLine("Replaced: " + s);

        // StringBuilder
        StringBuilder sb = new StringBuilder("Welcome");
        sb.Append(" to C#");
        Console.WriteLine("StringBuilder Append: " + sb);
        sb.Insert(0, "Hi! ");
        Console.WriteLine("After Insert: " + sb);
        sb.Replace("C#", "Programming");
        Console.WriteLine("After Replace: " + sb);
    }
}