C# 转换泛型类型(如 C++ 用户定义的转换)

Question

C# 中有没有一种方法可以为泛型类型执行用户定义的转换？

例如:

class Stack<T> 
{
    private T x; //should be an array but doesn't matter for this example

    public Stack(T input)
    {
        x = input;
    }

    public Stack<Q> Convert<Q>(Stack<T> inputStack)
    {
        //what would go here ? The call is below.
    }
}

//main code
Stack<int> stack = new Stack<int>(2);
Stack<long> longstack = stack.Convert<long>(stack);

我想编译器可以在 Convert 函数中推断出 Q 是 long 而 T 是 int，但它似乎不起作用。

Answer 1

不，因为类级泛型类型参数无法从用法中自动推断出来。

I would imagine that the compiler can deduce that Q is long and T is int in the Convert function, but it doesn't seem to work.

也许吧，但归根结底，泛型类型参数不属于构造函数。也就是说，您根据什么构造函数参数/参数为类型提供通用参数？如果不止一个构造函数参数会怎样？

public class A<T>
{
    // Which one should be used to auto-infer T from usage?
    // Maybe the integer? Or the bool? Or just the string...?
    // Every choice seems a joke, because it would be absolutely
    // arbitrary and unpredictable...
    public A(int x, string y, bool z)
    {
    }
}

现在以您的示例代码为例。它有同样的问题:应该从您的 Convert 静态方法中使用什么参数来从用法中推断泛型类型参数？如果 Convert 有多个参数...会怎样？