为什么代表可以互换使用Class方法和静态函数？ [英] Why can delegates can be used interchangeably for Class methods and Static functions?

问题描述

我一直在使用代表多年，并没有真正给予他们很多的想法。
但是我最近在我的脸上收到了蛋，假设委托人在引用类方法时在签名中包含一个这个引用。
下面的例子说明了我的理解差距。

  public class SomeClass 
 {
 public SomeClass（int someProperty）
 {
 SomeProperty = someProperty; 
} 
 
 public int SomeProperty 
 {
 get; 
设置; 
} 
 
 //在会员字段中投入混合
 public int ClassAdd（int x，int y）
 {
 return x + y + SomeProperty; 
} 
} 
 
 public static class SomeStaticClass 
 {
 public static int StaticAdd（int x，int y）
 {
返回x + y; 
} 
} 
  

为什么我可以添加静态和实例订阅者？

  delegate int addDelegate（int x，int y）; 
 
 class TestClass 
 {
 delegate int addDelegate（int x，int y）; 
 
 private void useDelegates（）
 {
 addDelegate algorithm; 
 algorithm = SomeStaticClass.StaticAdd; 
 algorithm + = new SomeClass（3）.ClassAdd; 
 
 int answer = algorithm（5，10）; 
} 
} 
  

上？ ;）

解决方案

如果创建一个引用一个实例方法的委托，它将捕获 code>（或相关参考）在后台支持 目标 属性的委托。如果创建一个引用静态方法的委托，则 Target 将为null。逻辑上，如果您使用静态方法，则无需实例。

由于增加了一些并发症，您可以将扩展名方法捕获为如果它们是扩展类型的实例方法：

  static class Extensions 
 {
 public static void Foo （这个字符串x）
 {
 Console.WriteLine（Calling Foo on+ x）; 
} 
} 
 
 class Test 
 {
 static void Main（）
 {
 Action action =text。 oo 
 Console.WriteLine（action.Target）; //打印text
} 
} 
  

至于为什么可以执行以下所有操作：因为它很有用，并且没有理由不允许您执行此操作：

I've been using delegates for many years, and haven't really given them much thought. But I recently got egg on my face by assuming that delegates included a this reference in the signature when referencing a class method. The below example illustrates the gap in my understanding.

public class SomeClass
{
    public SomeClass(int someProperty)
    {
        SomeProperty = someProperty;
    }

    public int SomeProperty
    { 
        get; 
        set; 
    }

    // Throw in a Member field into the mix
    public int ClassAdd(int x, int y)
    {
        return x + y + SomeProperty;
    }
}

public static class SomeStaticClass
{
    public static int StaticAdd(int x, int y)
    {
        return x + y;
    }
}

Why is it that I can add both static and instance subscribers?

    delegate int addDelegate(int x, int y);

    class TestClass
    {
        delegate int addDelegate(int x, int y);

        private void useDelegates()
        {
            addDelegate algorithm;
            algorithm = SomeStaticClass.StaticAdd;
            algorithm += new SomeClass(3).ClassAdd;

            int answer = algorithm(5, 10);
        }
    }

What is actually going on? ;)

解决方案

If you create a delegate referring to an instance method, it will capture this (or the relevant reference) in the field backing the Target property of the delegate. If you create a delegate referring to a static method, the Target will be null. Logically there's no need to have an instance if you're using a static method.

As one added complications, you can capture extension methods as if they were instance methods on the extended type:

static class Extensions
{
    public static void Foo(this string x)
    {
        Console.WriteLine("Calling Foo on " + x);
    }
}

class Test
{
    static void Main()
    {
        Action action = "text".Foo;
        Console.WriteLine(action.Target); // Prints "text"
    }
}

As for why you can do all of this: because it's useful, and there's no reason not to allow you to do it :)

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