C# 函数和可选参数

Question

I know that in C# it is possible to define optional parameters. My question is directed at how flexible this is.

Let f be a function as below, with a mandatory and b , c optional:

class Test {
   public void f(int a, int b = 2, int c = 3) {
      //...
   }
}

Now, I know I can call the function in the following ways:

f(1) -> a equals 1, b equals 2, c equals 3

f(11,22) -> a equals 11, b equals 22, c equals 3

f(11,22,33) -> a equals 11, b equals 22, c equals 33

How do I do to not specify b , but a and c ?

Answer 1

Try:

f(11, c: 33)

And take a look at the documentation

Answer 2

您可以在参数前添加参数名称：

f(1, c:3);

Answer 3

Using named arguments :

f(a: 5, c: 6);

Although, strictly speaking in my example, you don't have to qualify the a:

f(5, c: 6);

Answer 4

Another possibility would be to define the method with other parameters and call the original one with them using this syntax:

public void f(int a, int c = 3) => f(a, 2, c)

More comfortable usability if you call it, but gets fiddly to define if you have more than 2 optional parameters.

Answer 5

您使用命名参数：

f( a:100, c:300);