Constructor:
1. The Constructor is the first method that is run when an instance of a type is created. In visual basic a constructor is always Sub new ().
2. Constructor are use to initialize class and structure data before use. Constructor never returns a value and can be overridden to provide custom initialization functionality.
3. The constructor provides a way to set default values for data or perform other necessary functions before the object available for use.
Destructor:
Destructors are called just before an object is destroyed and can be used to run clean-up code. You can’t control when a destructor is called.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may
be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
Destructor and finalize
Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over the destructors.
In C# you can never call them, the reason is one cannot destroy an object. So who has the control over the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance.
6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction.
7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to least derived.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconfinalizemethodscdestructors.asp
What is the difference between Finalize and Dispose (Garbage collection)
Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object.
In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object. Dispose can be called even if other references to the object are alive.
Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose.
Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?
(Class constructor method is also known as type constructor or type initializer)
Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention.
A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is created or any static members are referenced.
1. The Constructor is the first method that is run when an instance of a type is created. In visual basic a constructor is always Sub new ().
2. Constructor are use to initialize class and structure data before use. Constructor never returns a value and can be overridden to provide custom initialization functionality.
3. The constructor provides a way to set default values for data or perform other necessary functions before the object available for use.
Destructor:
Destructors are called just before an object is destroyed and can be used to run clean-up code. You can’t control when a destructor is called.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may
be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
Destructor and finalize
Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over the destructors.
In C# you can never call them, the reason is one cannot destroy an object. So who has the control over the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method.
Points to remember:
1. Destructors are invoked automatically, and cannot be invoked explicitly.
2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor.
3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it.
4. Destructors cannot be used with structs. They are only used with classes.
5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance.
6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction.
7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to least derived.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconfinalizemethodscdestructors.asp
What is the difference between Finalize and Dispose (Garbage collection)
Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object.
In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object. Dispose can be called even if other references to the object are alive.
Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose.
Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?
(Class constructor method is also known as type constructor or type initializer)
Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention.
A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is created or any static members are referenced.
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