如何调用泛型方法与类型约束时，参数没有这些限制？ [英] How to call a generic method with type constraints when the parameter doesn't have these constraints?

问题描述

class A { }
interface I { }
void GenericStuff<T>(T x) { }
void SpecificStuff<T>(T x) where T : A, I { }

void Start<T>(T x)
{
    if (x is A && x is I)
        SpecificStuff(x); // <---- Wrong type
    else
        GenericStuff(x);
}

我已经得到了上面显示的情况。在方法开始（）我得到一个参数 X ，并根据它的类型我想打电话给任 GenericStuff（）或 SpecificStuff（）方法。当然，类型约束$ P $这样做pvent我，因为有两个人，我不能让他们身边通过铸造。

I've got the situation illustrated above. In method Start() I get a single parameter x and depending on it's type I want to call either the GenericStuff() or the SpecificStuff() method. Naturally, the type constraints prevent me from doing so, and since there are two of them, I cannot get around them by casting.

有什么办法（反射短）来完成这项工作？

Is there any way (short of reflection) to accomplish this?

推荐答案

您可以使用动态。虽然这或多或少是荣耀的反映，它看起来更漂亮：

You can use dynamic. While this is more or less glorified reflection, it looks much nicer:

void Start<T>(T x)
{
    if (x is A && x is I)
        SpecificStuff((dynamic)x);
    else
        GenericStuff(x);
}

请注意：
如果在以后，你改变 SpecificStuff 的类型约束，以包含第三个界面，你忘了更新你的如果因此，您将获得运行时异常，而不是编译时错误。

Please note:
If, at a later point, you change the type constraints of SpecificStuff to contain a third interface and you forget to update your if accordingly, you will get runtime exceptions and not compile time errors.

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