A detailed analysis of the use of New in C # and the difference between it and override

This article mainly introduces the use of New in C #, and the difference with override, the need for friends can refer to the following

There are three ways to use New in C #:

(1) New is an operator that is used to create objects and invoke constructors. such as Class1=new Class1 (); You can also call the default constructor for a value type, such as int a=new int (), at which time a=0.

(2) New is a modifier that hides the inherited members of a base class member. Override cannot hide inherited members that accumulate members. Such as:

Using system;using system.collections.generic;using system.linq;using system.text;namespace A{    class Program  {    Abstract public class Test    {public            virtual void Prinf ()       {        Console.WriteLine ("Abstract Printf ... ");}    public class Class1:test    {public            override void Prinf ()       {        Console.WriteLine ("Class one override Printf ... ");}    public class Class2:test    {public      new void Prinf ()      {        Console.WriteLine ("Class-New Printf ...");      }    }         static void Main (string[] args)    {      Class1 cls1 = new Class1 ();      Class2 cls2 = new Class2 ();      Cls1. Prinf ();      Cls2. Prinf ();      (Test) CLS1). Prinf ();      (Test) CLS2). Prinf ();      Console.ReadLine ();}}}  

The result of the operation shows that the new modifier hides the overriding method, invoking the method of the base class by turning the derived object into a base class object. Override, however, is a complete rewrite of the method, even if it is called to the base class object, which is also the overridden method of the derived class.

That is: New hides the base class method, override overrides the base class method.

(3) New is a constraint. A constraint that adds a type to a generic type.

Using system;using system.collections.generic;using system.linq;using system.text;namespace A{  class Test<T >    where T:new ()//Defines the constraint of type T, which means that the T type must have a constructor without parameters  {public    T GetItem ()    {      return new T ();//If you do not add new () constraint, compile error: Variable type ' T ' does not have a new () constraint, so an instance of the type cannot be created              //think about it, the T type does not know that the compiler does not know how much space is allocated, so it is implemented by reflection technology    }  }  class Tclass  {    private int A;        Public Tclass ()//If no parameterless constructor is added, compile error: Tclass must be a non-abstract type with a common parameterless constructor to be used as the parameter "T"    {} in the generic type or method "A.test<t>"    Public    tclass (int a)    {      THIS.A = A;    }  }  Class program  {      static void Main (string[] args)    {      test<tclass> Test = new test<tclass> ();      Console.ReadLine ();}}}