具有可选参数的冲突重载方法 [英] Conflicting overloaded methods with optional parameters

问题描述

我有两种重载方法，一种带有可选参数.

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

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

现在我打电话:

 foo("abc");

有趣的是，调用了第一个重载.为什么不将可选值设置为零的第二个重载?

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

老实说，我原以为编译器会带来错误，至少是警告，以避免无意中执行错误的方法.

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# 团队这样定义它?

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

推荐答案

来自 MSDN:

如果两个候选人被判断为同样好，则优先选择没有可选参数的候选人，这些参数在调用中被省略.这是由于参数较少的候选者在重载决议中普遍偏爱的结果.

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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