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As the output verifies, i is initialized to zero Remember, without the use of new, i would be uninitialized, and it would cause an error to attempt to use it in the WriteLine( ) statement without explicitly giving it a value first In general, invoking new for a value type invokes the default constructor for that type It does not, however, dynamically allocate memory Frankly, most programmers do not use new with the value types

As you have seen, objects are dynamically allocated from a pool of free memory by using the new operator Of course, memory is not infinite, and the free memory can be exhausted Thus, it is possible for new to fail because there is insufficient free memory to create the desired object For this reason, one of the key components of any dynamic allocation scheme is the recovery of free memory from unused objects, making that memory available for subsequent reallocation In many programming languages, the release of previously allocated memory is handled manually For example, in C++, the delete operator is used to free memory that was allocated However, C# uses a different, more trouble-free approach: garbage collection C# s garbage collection system reclaims objects automatically occurring transparently, behind the scenes, without any programmer intervention It works like this: When no references to an object exist, that object is assumed to be no longer needed, and the memory occupied by the object is eventually released and collected This recycled memory can then be used for a subsequent allocation Garbage collection occurs only sporadically during the execution of your program It will not occur simply because one or more objects exist that are no longer used Thus, you can t know, or make assumptions about, precisely when garbage collection will take place

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It is possible to define a method that will be called just prior to an object s final destruction by the garbage collector This method is called a destructor, and it can be used in some highly specialized situations to ensure that an object terminates cleanly For example, you might use a destructor to ensure that a system resource owned by an object is released It must be stated at the outset that destructors are a very advanced feature that are applicable only to certain rare cases They are not normally needed They are briefly described here for completeness Destructors have this general form: ~class-name( ) { // destruction code }

Part I:

Here, class-name is the name of the class Thus, a destructor is declared like a constructor except that it is preceded with a ~ (tilde) Notice it has no return type and takes no arguments To add a destructor to a class, you simply include it as a member It is called whenever an object of its class is about to be recycled Inside the destructor, you will specify those actions that must be performed before an object is destroyed It is important to understand that the destructor is called just prior to garbage collection It is not called when a variable containing a reference to an object goes out of scope, for example (This differs from destructors in C++, which are called when an object goes out of scope) This means that you cannot know precisely when a destructor will be executed Furthermore, it is possible for your program to end before garbage collection occurs, so a destructor might not get called at all The following program demonstrates a destructor It works by creating and destroying a large number of objects During this process, at some point the garbage collector will be activated, and the destructors for the objects will be called

// Demonstrate a destructor using System; class Destruct { public int x; public Destruct(int i) { x = i; } // Called when object is recycled ~Destruct() { ConsoleWriteLine("Destructing " + x); } // Generates an object that is immediately destroyed public void Generator(int i) { Destruct o = new Destruct(i); } } class DestructDemo { static void Main() { int count; Destruct ob = new Destruct(0); /* Now, generate a large number of objects At some point, garbage collection will occur Note: You might need to increase the number of objects generated in order to force garbage collection */ for(count=1; count < 100000; count++)