static void Main(string[] args)
  {
      String c = "Hello i love you";
      String a ;
      a = c.Substring(12, 3);
      Console.WriteLine(a);
      Console.ReadLine();
  }

a) 
   String a = "She sold her beauty in one night to someone else";
   int i;
   i = a.SecondIndexOf("s");

b) 
   String a = "She sold her beauty in one night to someone else";
   int i, j;
   i = a.FirstIndexOf("s");
   j = a.IndexOf("s", i + 1);

c) 
   String a = "She sold her beauty in one night to someone else";
   int i, j;
   i = a.IndexOf("s");
   j = a.IndexOf("s", i + 1);

static void main(String args[])
 {
     char chars[] = {'x', 'y', 'z'};
     String s = new String(chars);
     Console.WriteLine(s);
 }

static void Main(string[] args)
 {
     StringBuilder s = new StringBuilder("object");
     s./*______*/("Oriented Language");
     Console.WriteLine(s);
     Console.ReadLine();
 }
Output : objectOriented Language

static void Main(string[] args)
  {
      string s = " i love you";
      Console.WriteLine(s.IndexOf('l') + "  " + s.lastIndexOf('o') + "  " + s.IndexOf('e'));
      Console.ReadLine();
  }

static void Main(string[] args)
 {
     string c = "hello";
     string  c1 = c.Remove(1);
     Console.WriteLine(c1);
     Console.ReadLine();
 }