使用可选参数冲突重载方法 [英] Conflicting overloaded methods with optional parameters

问题描述

我有两个重载方法，一个有可选参数。

I have two overloaded methods, one with an optional parameter.

void foo(string a)  { }  
void foo(string a, int b = 0) { }  

现在我调用：

 foo("abc");

有趣的是，第一个重载被调用。
为什么不是第二个重载的可选值设置为零？

interestingly the first overload is called. why not the second overload with optional value set to zero?

说实话，我希望编译器带来一个错误，至少一个警告以避免无意的执行错误的方法。

To be honest, I would have expect the compiler to bring an error, at least a warning to avoid unintentional execution of the wrong method.

这种行为的原因是什么？为什么C＃团队会这样定义？

What's the reason for this behaviour? Why did the C# team define it that way?

推荐答案

从 MSDN ：

如果两个候选人被判定为同样好，首选项转到没有可选参数的候选项，其参数在调用中被省略。这是对具有较少参数的候选者的重载解析的一般偏好的结果。

If two candidates are judged to be equally good, preference goes to a candidate that does not have optional parameters for which arguments were omitted in the call. This is a consequence of a general preference in overload resolution for candidates that have fewer parameters.

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