为什么我不能定义隐式和显式运算符？

Why I cannot define both implicit and explicit operators like so?

为什么我不能像这样定义隐式和显式运算符?

    public class C
    {
        public static implicit operator string(C c)
        {
            return "implicit";
        }

        public static explicit operator string(C c)
        {
            return "explicit";
        }
    }

You can do this hack though :)

你可以这样做虽然:)

    class Program
    {
        public class A
        {

        }

        public class B
        {
            public static implicit operator A(B b)
            {
                Console.WriteLine("implicit");
                return new A();
            }
        }

        public class C : B
        {
            public static explicit operator A(C c)
            {
                Console.WriteLine("explicit");
                return new A();
            }
        }

        static void Main(string[] args)
        {
            C c = new C();

            A a = c;
            A b = (A) c;
        }
    }

This prints:

implicit
explicit

2 个解决方案

#1

Check this: Why can't coexist implicit and explicit operator of the same type in C#?

检查一下:为什么不能在C#*存相同类型的隐式和显式运算符?

If you define an explicit operator, you will be able to do something like this:

如果您定义一个显式运算符,您将能够执行以下操作:

Thing thing = (Thing)"value";

If you define an implicit operator, you can still do the above, but you can also take advantage of implicit conversion:

如果您定义了隐式运算符,您仍然可以执行上述操作,但您也可以利用隐式转换:

Thing thing = "value";

In short, explicit allows only explicit conversion, while implicit allows both explicit and implicit... hence the reason why you can only define one.

简而言之,explicit只允许显式转换,而implicit允许显式和隐式......因此你只能定义一个。

#2

I don't know the technical limitation that prevents this, but I think they would have done this to prevent people from shooting their own feet off.

我不知道阻止这种情况的技术限制,但我认为他们会这样做是为了防止人们自己开枪。

string imp = new C(); // = "implicit"
string exp = (string)new C(); // = "explicit"

That would drive me bonkers and makes no sense, C should only cast to a string 1 way, not 2 different ways.

这会让我感到疯狂,没有任何意义,C只应该以一种方式投射到一个字符串,而不是两种不同的方式。

#1