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C# LANGUAGE SPECIFICATION

destructor-declaration: attributesopt   externopt   ~   identifier   (   )    destructor-body

destructor-body: block ;

A destructor-declaration may include a set of attributes (§‎17).

The identifier of a destructor-declarator must name the class in which the destructor is declared. If any other name is specified, a compile-time error occurs.

When a destructor declaration includes an extern modifier, the destructor is said to be an external destructor. Because an external destructor declaration provides no actual implementation, its destructor-body consists of a semicolon. For all other destructors, the destructor-body consists of a block which specifies the statements to execute in order to destruct an instance of the class. A destructor-body corresponds exactly to the method-body of an instance method with a void return type (§‎10.5.8).

Destructors are not inherited. Thus, a class has no destructors other than the one which may be declared in that class.

Since a destructor is required to have no parameters, it cannot be overloaded, so a class can have, at most, one destructor.

Destructors are invoked automatically, and cannot be invoked explicitly. An instance becomes eligible for destruction when it is no longer possible for any code to use that instance. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction. When an instance is destructed, the destructors in that instance’s inheritance chain are called, in order, from most derived to least derived. A destructor may be executed on any thread. For further discussion of the rules that govern when and how a destructor is executed, see §‎3.9.

The output of the example

using System;

class A { ~A() { Console.WriteLine("A's destructor"); } }

class B: A { ~B() { Console.WriteLine("B's destructor"); } }

class Test {   static void Main() { B b = new B(); b = null; GC.Collect(); GC.WaitForPendingFinalizers();   } }

is

258Copyright Microsoft Corporation 1999-2003. All Rights Reserved.

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