using System;
   
public interface IPrintMessage
{
    void Print();
};
   
class Class1
{
    public void Print()
    {
        Console.WriteLine("Hello from Class1!");
    }
}
   
class Class2 : IPrintMessage
{
    public void Print()
    {
        Console.WriteLine("Hello from Class2!");
    }
}
   
class MainClass
{
    public static void Main()
    {
        PrintClass   PrintObject = new PrintClass();
   
        PrintObject.PrintMessages();
    }
}
   
class PrintClass
{
    public void PrintMessages()
    {
        Class1      Object1 = new Class1();
        Class2      Object2 = new Class2();
   
        PrintMessageFromObject(Object1);
        PrintMessageFromObject(Object2);
    }
   
    private void PrintMessageFromObject(object obj)
    {
        IPrintMessage PrintMessage;
   
        PrintMessage = obj as IPrintMessage;
        if(PrintMessage != null)
            PrintMessage.Print();
    }
}

    

   
 


using System;
   
class Employee { }
   
class ContractEmployee : Employee { }
   
class CastExample5
{
    public static void Main ()
    {
        Employee e = new Employee();
        Console.WriteLine("e = {0}", e == null ? "null" : e.ToString());
   
        ContractEmployee c  = e as ContractEmployee;
        Console.WriteLine("c = {0}", c == null ? "null" : c.ToString());
    }
}

    

   

// Demonstrate a using alias. 
 
using System; 
 
// Create an alias for Counter.CountDown. 
using Count = Counter.CountDown; 
 
// Declare a namespace for counters. 
namespace Counter { 
  // A simple countdown counter. 
  class CountDown { 
    int val; 
 
    public CountDown(int n) { 
      val = n; 
    } 
 
    public void reset(int n) { 
      val = n; 
    } 
 
    public int count() { 
      if(val > 0) return val--; 
      else return 0; 
    } 
  } 
} 
 
public class NSDemo4 { 
  public static void Main() { 
    // Here, Count is used as a name for Counter.CountDown. 
    Count cd1 = new Count(10); 
    int i; 
 
    do { 
      i = cd1.count(); 
      Console.Write(i + " "); 
    } while(i > 0); 
    Console.WriteLine(); 
 
    Count cd2 = new Count(20); 
 
    do { 
      i = cd2.count(); 
      Console.Write(i + " "); 
    } while(i > 0); 
    Console.WriteLine(); 
 
    cd2.reset(4); 
    do { 
      i = cd2.count(); 
      Console.Write(i + " "); 
    } while(i > 0); 
    Console.WriteLine(); 
  } 
}

           
          

   

/*
C# Programming Tips & Techniques
by Charles Wright, Kris Jamsa

Publisher: Osborne/McGraw-Hill (December 28, 2001)
ISBN: 0072193794
*/
// Alias.cs -- demonstrates using an alias to resolve ambiguity
//
//             Compile this program with the following command line:
//                 C:>csc Alias.cs
using System;
using MsgBox = System.Windows.Forms.MessageBox;
using System.Timers;

namespace nsNamespaces
{
    public class Alias
    {
        static Timer timer;
        static public void Main ()
        {
            // Create the timer object.
            timer = new Timer (2000);
            
            // This is a one-shot timer. Set auto reset to false
            timer.AutoReset = false;
            
            // Assign the event handler method.
            timer.Elapsed += new ElapsedEventHandler(ProcessTimerEvent);
            
            // Start the timer.
            timer.Start ();
            
            // Wait for the timeout to occur.
            MsgBox.Show ("Waiting for timer to expire", "Text");
        }

        // Timer event handler.
        private static void ProcessTimerEvent (Object obj, ElapsedEventArgs e)
        {
            MsgBox.Show ("The timer has expired. Press "OK" " +
                         " to terminate the program",
                         "Timer Expired");
            timer.Close ();
            Environment.Exit (0);
        }
    }
}