C#4.0以及可选参数和重载的组合是否会向您发出有关歧义的警告? [英] Does C# 4.0 and a combination of optional parameters and overloads give you a warning about ambiguity?

问题描述

我已经开始阅读乔恩·斯凯特(Jon Skeet)的书的早期版本，其中包含有关C#4.0的各个部分，有一件事令我震惊.不幸的是，我没有Visual Studio 2010，因此我想我只是在这里问一下，看看是否有人知道答案.

I've started reading Jon Skeet's early access version of his book, which contains sections on C# 4.0, and one thing struck me. Unfortunately I don't have Visual Studio 2010 available so I thought I'd just ask here instead and see if anyone knew the answer.

如果我有以下代码，请结合使用现有代码和新代码:

If I have the following code, a mixture of existing code, and new code:

public void SomeMethod(Int32 x, Int32 y) { ... }

public void SomeMethod(Int32 x, Int32 y, Int32 z = 0) { ... }

编译器会在定义站点还是在调用站点抱怨可能存在的歧义?

Will the compiler complain either at the definition site or the call site about possible ambiguity?

例如，这段代码实际上将做什么?

For instance, what will this piece of code actually do?

SomeClass sc = new SomeClass();
sc.SomeMethod(15, 23);

会编译吗?它会调用不带z参数的那个，还是会调用带z参数的那个?

Will it compile? Will it call the one without the z parameter, or will it call the one with the z parameter?

推荐答案

它将在没有警告的情况下进行编译，并将选择第一个重载.

It will compile without warnings and will choose the first overload.

随着可选参数和命名参数的引入，C#的重载解析机制变得非常复杂.但是，在这种特定情况下，这是有道理的.与往常一样，编译器将选择与参数匹配的最具体的重载.

With the introduction of optional and named parameters, the overload resolution mechanism of C# has become really complicated. In this specific case, it makes sense however. As usual, the compiler will choose the most specific overload that matches the arguments.

我不认为此特定情况与C#1.0有什么大不同:

I don't believe this specific case is much different from C# 1.0:

public void SomeMethod(Int32 x, Int32 y) { } 
public void SomeMethod(Int32 x, Int32 y, params Int32[] z) { }

(在重载分辨率方面)工作原理相同.

which works identically (in terms of overload resolution).

关注答案:我不这样认为.恐怕您将不得不在方法调用中手动指定默认参数.但是，如果x或y参数具有不同的名称，例如:

Follow up answer: I don't think so. I'm afraid you'll have to manually specify the default argument in the method call. However, if x or y parameter had a different name like:

public void SomeMethod(Int32 x, Int32 y) { } 
public void SomeMethod(Int32 t, Int32 y, Int32 z = 0) { }

您可以选择第二个过载:

you could choose the second overload with:

obj.SomeMethod(t: 10, y: 20);

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