What's the Difference Between `new` and `override` in C# Inheritance?

C# Inheritance: Understanding new and override

In C# inheritance, the keywords new and override offer distinct ways to manage method behavior in derived classes. This explanation clarifies their differences and appropriate usage.

new Modifier: Defining a Separate Method

The new modifier allows a derived class to introduce a method with the same name as a method in its base class. Crucially, this does not override the base class method; instead, it creates a completely independent method.

Example:

<code class="language-csharp">public class BaseClass {
    public void MyMethod() { Console.WriteLine("BaseClass Method"); }
}

public class DerivedClass : BaseClass {
    public new void MyMethod() { Console.WriteLine("DerivedClass Method"); }
}</code>

Here, DerivedClass.MyMethod() is a distinct method. Calling MyMethod() on a DerivedClass instance executes the derived class's version; calling it on a BaseClass instance executes the base class's version.

override Modifier: Replacing a Virtual Method

The override modifier is used to replace the implementation of a virtual method from the base class. The base class method must be declared as virtual (or abstract). override ensures the derived class's version is called when the method is invoked on an instance of the derived class.

Example:

<code class="language-csharp">public class BaseClass {
    public virtual void MyMethod() { Console.WriteLine("BaseClass Method"); }
}

public class DerivedClass : BaseClass {
    public override void MyMethod() { Console.WriteLine("DerivedClass Method"); }
}</code>

In this case, DerivedClass.MyMethod() overrides BaseClass.MyMethod(). Calling MyMethod() on a DerivedClass instance always executes the DerivedClass version.

Key Differences Summarized:

Feature

Feature	new	override
Method Creation	Creates a completely new method	Replaces an existing virtual method
Inheritance	Breaks the inheritance chain for the method	Maintains the inheritance chain
Base Class Method	Base class method remains unaffected	Base class method must be virtual/abstract

Method Creation

Creates a completely new method

Replaces an existing virtual method

Inheritance

Breaks the inheritance chain for the method

Maintains the inheritance chain

Base Class Method

Base class method remains unaffected

Base class method must be virtual/abstract

When to Use Each Modifier:

• Use new when you want a completely separate method in the derived class, even if it shares a name with a method in the base class. This is useful for avoiding unintended overriding and maintaining distinct functionality.

• Use override when you intend to extend or modify the behavior of a virtual method defined in the base class, providing a specialized implementation within the derived class while still maintaining the inheritance relationship for that specific method.

By understanding these distinctions, you can effectively utilize inheritance and polymorphism in your C# applications.

The above is the detailed content of What's the Difference Between `new` and `override` in C# Inheritance?. For more information, please follow other related articles on the PHP Chinese website!