为什么使用“new DelegateType(Delegate)"? [英] Why use "new DelegateType(Delegate)"?

问题描述

好的，假设您在某个类中定义了一个委托.

Ok, suppose you define a delegate in some class.

public delegate void StringDelegate (string s);

另一个类实现了一个方法:

and another class implements a method :

public static void StringWriter (string s) {...}

在我正在阅读Programming C#"第 4 版的书中，他们使用 new 关键字创建委托，例如:

In the book that I'm reading "Programming C#" 4th ed they create delegates using the new keyword, ex:

ClassDelegate.StringDelegate writer;
writer = new ClassDelegate.StringDelegate (DelegateImplementer.StringWriter);
writer("Hello");

不过，我看到也可以这样调用委托方法

However, I see one can also call the delegate method this way

ClassDelegate.StringDelegate writer;
writer = DelegateImplementer.StringWriter;
writer ("Hello");

有什么区别?当我可以简单地传递或引用方法委托的签名时，为什么还要实例化并创建一个对象委托.

What's the difference? Why do I want instantiate and create an object delegate when I can just simply pass or make reference to the signature of the method delegate.

推荐答案

这两种说法绝对没有区别.writer = DelegateImplementer.StringWriter; 仍然创建一个 delegate 对象；编译器将为您生成 new ClassDelegate.StringDelegate ().这只是 在 C# 2.0 中添加的更简洁的语法.

There is absolutely no difference between the two statements. writer = DelegateImplementer.StringWriter; still creates a delegate object; the compiler will generate the new ClassDelegate.StringDelegate () for you. It's just a cleaner syntax that was added in C# 2.0.

正如@Ben Voigt 在他的回答中提到的，只有在使用 Control.Invoke() 例如.

As @Ben Voigt mentioned in his answer is only required in C# 2.0 where the compiler can't deduce the type of the delegate, when using Control.Invoke() for example.

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