Does C# Support Return Type Covariance, and How Can It Be Achieved?

The return type of collaboration in the return type: support and implementation

The return type in the c#allows the derivative class to return a more specific type than its base class. This feature makes it possible to create a method that can provide both professional behaviors and maintain the integrity of hierarchical structure.

Let's take a look at an example:

In this scene, there is a method of returning a string in the

<code class="language-csharp">public abstract class Animal
{
    public abstract string GetName();
}

public class Cat : Animal
{
    public string GetMeow();
}</code>

class to specify that its meow call will be very useful. However, C#does not directly support the return type coordination.

Cat In the initial answer in 2011, C#did not support returning types of collaborative changes, and due to the restrictions of public languages ​​(CLR), it was unlikely to realize it in the future. However, in the latest version of C#, this situation has changed. See the link article, "

https://www.php.cn/link/40F4D60542D86344E5711c7a5584832

The collaborative return", understand how to achieve more information about the return type collaboration in the C# 9.0 and the higher versions Essence Before the introduction of the return type co -changes, one solution is to introduce an intermediate method to obtain the return value of the derived class.

This technology allows a specific

<code class="language-csharp">public abstract class Animal
{
    public abstract object GetContents();
    public Animal Contents() { return (Animal)GetContents(); }
}

public class Cat : Animal
{
    protected override object GetContents() { return this; }
    public new string Contents() { return GetMeow(); }
}</code>

to retrieve

, and return a string in this example. Cat Contents Although the version before C# 9.0 does not directly support the return type coordination, the solution discussed can still be used as a method to realize the required behavior. However, it should be noted that in the higher version of C#, the formal implementation of the return type coordination provides a more elegant and more concise solution.

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