The usage of virtual and new keywords in

in C# In object -oriented programming, it is usually defined in the base class, and these methods are rewritten or redefined in the derivative class. Although both "Virtual" and "New" keywords can be used to modify the method declaration, they have different implementation methods.

dirtual rewriting

The method declared in the base class as "virtual", indicating that subclasses can be rewritten.

Allow derived classes to provide different methods for implementation without destroying the inheritance chain.
• New keyword

State a new method of the same name as the foundation Chinese method in the derivative class.

Hide the basic method and create a new implementation in the derived class.

• Destroy the inheritance chain, which means that the derived method is not related to the base method.
Example

Consider the following code:

Public Class Base {{ public virtual bool dosomething () {Return false;} } Public class derived: base: base {{ Public override bool dosomething () {Return True;} }

If we create a Derived instance and store it in the base type variable, the call for Dosomething () will call the method of rewriting in Derived:

public class Base
{
    public virtual bool DoSomething() { return false; }
}

public class Derived : Base
{
    public override bool DoSomething() { return true; }
}

On the contrary, if we use the new keyword in Derived, the call for dosomething () will call a new method in Derived. Even if the variable is Base type:

Base a = new Derived();
a.DoSomething(); // 返回 true

base a = new derived (); a.dosomething (); // Return to True (new method in derived)

public class Derived : Base
{
    public new bool DoSomething() { return true; }
}

Base a = new Derived();
a.DoSomething(); // 返回 true (Derived 中的新方法)