在静态类的静态方法的参数中使用此参数? [英] Using this in parameters of static methods in static class?

问题描述

为什么我应该在静态类的静态函数中对参数对象使用'this'?我的意思是使用这两种方法的真正区别是什么?

Why should I use 'this' in static functions of static classes to objects in parameter? I mean is the real difference between using those 2 methods?

public static class Extensions
{
    public static string AsJson(this object obj)
    public static string AsJson2(object obj)
}

推荐答案

public static string AsJson(this object obj)

它是 扩展方法 在 object

扩展方法被定义为静态方法，但由调用使用实例方法语法.他们的第一个参数指定了键入要对其进行操作的方法，并且参数之前是此修饰符.

您的其他方法只是一个简单的静态方法.

Your other method is just a simple static method.

public static string AsJson2(object obj)

他们的两个通话都将是:

Both of their calls would be like:

Object obj = new object();
string str = obj.AsJson(); //extension method called

string str2  = Extensions.AsJson2(obj); //Normal static method called

string str3 = Extensions.AsJson(obj); //extension method called like a normal static method

扩展方法的调用类似于实例方法，但是编译器实际上转换为对静态方法的调用

Extension methods are called like instance method but the compiler actually translates into a call to Static method

但是，编译器生成的中间语言(IL)将您的代码转换为对静态方法的调用.

However, the intermediate language (IL) generated by the compiler translates your code into a call on the static method.

所以

string str = obj.AsJson(); 

翻译成

string str = Extensions.AsJson(obj);

这就是为什么您可以这样做:

That is why you can actually do:

object obj = null;
obj.AsJosn(); //Would not result in NRE

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