Introduction

In the enterprise application development world, the buzzwords are Performance, Scalability, and Security. I started my career as a VC++ programmer, and one fine morning, I was transferred to Web development department. Like every C++ programmer, I also was frustrated. I thought every Tom, Dick, and our very own Harry can program in HTML. But, soon I found that the real challenge is to produce high performance, scalable, and reliable applications. And above all that the loosely coupled, stateless nature of web environment is always going to haunt you.

In order to produce high performance scalable applications, it is important to use your resources in an optimized manner. One tip is that use your resource as late as you can and free it at the earliest after your use. My intention here is to describe the object cleaning up mechanism used in C#.

Destructors

As we all know, ‘Destructors’ are used to destruct instances of classes. When we are using destructors in C#, we have to keep in mind the following things:

• A class can only have one destructor.
• Destructors cannot be inherited or overloaded.
• Destructors cannot be called. They are invoked automatically.
• A destructor does not take modifiers or have parameters.

The following is a declaration of a destructor for the class MyClass:

~ MyClass() 
{
   // Cleaning up code goes here
}

The programmer has no control on when the destructor is going to be executed because this is determined by the Garbage Collector. The garbage collector checks for objects that are no longer being used by the application. It considers these objects eligible for destruction and reclaims their memory. Destructors are also called when the program exits. When a destructor executes what is happening behind the scenes is that the destructor implicitly calls the Object.Finalize method on the object's base class. Therefore, the preceding destructor code is implicitly translated to:

protected override void Finalize()
{
   try
   {
      // Cleaning up .
   }
   finally
   {
      base.Finalize();
   }
}

Now, let us look at an example of how destructors are called. We have three classes A, B and C. B is derived from A, and C is derived from B. Each class has their own constructors and destructors. In the main of the class App, we create an object of C.

using System;
class A
{
 public A()
 {
  Console.WriteLine("Creating A");
 }
 ~A()
 {
  Console.WriteLine("Destroying A");
 }
}

class B:A
{
 public B()
 {
  Console.WriteLine("Creating B");
 }
 ~B()
 {
  Console.WriteLine("Destroying B");
 }

}
class C:B
{
 public C()
 {
  Console.WriteLine("Creating C");
 }

 ~C()
 {
  Console.WriteLine("Destroying C");
 }
}
class App
{
 public static void Main()
 {
  C c=new C();
  Console.WriteLine("Object Created ");
  Console.WriteLine("Press enter to Destroy it");
  Console.ReadLine();
  c=null;
  //GC.Collect();
  Console.Read();
 }

}

As we expect, the constructors of base classes will be executed and program will wait for the user to press 'enter'. When this occurs, we set the object of class C to null. But the destructors are not executing ..!!?? As we already said, the programmer has no control on when the destructor is going to be executed because the Garbage Collector determines this. But the destructors are called when the program exits. You can check this by redi