为什么新的Thread（）接受一个方法名，尽管没有一个构造函数重载似乎允许这样做？ [英] Why does new Thread() accept a method name, even though none of the constructor overloads seem to allow this?

问题描述

可能重复：
  <一href="http://stackoverflow.com/questions/10482121/what-is-the-difference-between-new-threadvoid-target-and-new-threadnew-thre">What是新的线程之间的差值（空目标（））和新主题（新的ThreadStart（空目标（）））？

我对Thread类的小问题。这个类有4构造函数：

I have a small question about Thread class. This class has 4 constructors:

public Thread(ParameterizedThreadStart start);
public Thread(ThreadStart start);
public Thread(ParameterizedThreadStart start, int maxStackSize);
public Thread(ThreadStart start, int maxStackSize);

我用的是第二个构造函数来创建Thread对象：

I use the 2nd constructor to create a Thread object:

Thread thread = new Thread(new ThreadStart(ScanDirectory));

不过，我可以用一种方式来创建这个对象，而无需使用我讲上面的任何构造函数。

However, I can use a way to create this object without using any constructors I talk above.

Thread thread = new Thread(ScanDirectory);

在这种情况下，ScanDirectory是一个无效的方法，它不是的ThreadStart或ParameterizedThreadStart但Thread类还是接受这个构造。为什么？ 我认为这是一个.NET功能，但我不知道它是如何实现的。

In this case, ScanDirectory is a void method, it isn't ThreadStart or ParameterizedThreadStart but Thread class still accepts this constructor. Why? I think this is a .NET feature but I don't know how it's implemented.

注意： ScanDirectory是一个无效的方法

Note: ScanDirectory is a void method.

推荐答案

据分开两件事很重要：

• 到线程调用构造
• 为代表的创造的通过的到发构造

• The call to the Thread constructor
• The creation of a delegate to pass to the Thread constructor

你的真正的兴趣，后者在这里 - 之间的区别：

You're really interested in the latter here - the difference between:

ThreadStart tmp = new ThreadStart(ScanDirectory);

和

ThreadStart tmp = ScanDirectory;

这些第二种是的方法组转换的 - 从方法组的（一个方法的名称，可能受限定的通过一个实例值，如果它是一个隐式转换实例方法）与兼容签名的委托。

The second of these is a method group conversion - an implicit conversion from a method group (the name of a method, possibly qualified by an instance value if it's an instance method) to a delegate with a compatible signature.

您很少需要明确的委托创作EX $ P $第一种形式的pssion，由于方法组转换是在C＃2，介绍你会看到很多code仍然使用它，因为很多开发者没有注意到方法组转换，遗憾的是 - 和IIRC Visual Studio的设计师仍然使用这种形式的事件处理程序订阅

You very rarely need the "explicit" delegate creation expression of the first form, since method group conversions were introduced in C# 2. You'll see a lot of code which still uses it because many developers are unaware of method group conversions, unfortunately - and IIRC the Visual Studio designers still uses that form for event handler subscription.

你真正需要的时候，方法组转换结束了模棱两可这是唯一的一次。例如：

The only time you'd really need it was when the method group conversion ended up being ambiguous. For example:

static void Main()
{
    // Valid: uses parameterless overload
    new Thread(new ThreadStart(Foo));

    // Valid: uses parameterized overload
    new Thread(new ParameterizedThreadStart(Foo));

    // Invalid, as there are two valid constructor overloads
    new Thread(Foo);
}

static void Foo()
{
}

static void Foo(object state)
{
}

这篇关于为什么新的Thread（）接受一个方法名，尽管没有一个构造函数重载似乎允许这样做？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！