| Code Example |
 // Factory Method
// Intent: "Provide a surrogate or placeholder for another object to
// control access to it".
// For further information, read "Design Patterns", p207, Gamma et al.,
// Addison-Wesley, ISBN:0-201-63361-2
  /**//* Notes:
 * When there is a large CPU/memory expense attached to handling an object
* directly, it can be useful to use a lightweight proxy in front of it,
* which can take its place until the real object is needed.
 */
namespace Proxy_DesignPattern
 {
using System;
using System.Threading;
  /**//// <summary>
/// Summary description for Client.
 /// </summary>
abstract class CommonSubject
{
abstract public void Request();
}
class ActualSubject : CommonSubject
{
public ActualSubject()
{
// Assume constructor here does some operation that takes quite a
// while - hence the need for a proxy - to delay incurring this
// delay until (and if) the actual subject is needed
Console.WriteLine("Starting to construct ActualSubject");
Thread.Sleep(1000); // represents lots of processing!
Console.WriteLine("Finished constructing ActualSubject");
}
override public void Request()
{
Console.WriteLine("Executing request in ActualSubject");
}
}
class Proxy : CommonSubject
{
ActualSubject actualSubject;
override public void Request()
{
if (actualSubject == null)
actualSubject = new ActualSubject();
actualSubject.Request();
}
}
public class Client
{
public static int Main(string[] args)
{
Proxy p = new Proxy();
// Perform actions here
// . . .
if (1==1) // at some later point, based on a condition,
p.Request();// we determine if we need to use subject
return 0;
}
}
}
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