如何知道type参数是否是动态的? [英] How to know if the type parameter is dynamic?

问题描述

似乎每次通用方法的调用者使用 dynamic 时，实际使用的类型都是一个简单的 object .例如，代码:

It seems that every time dynamic is used by the caller of a generic method, the type actually used is a simple object. For example, the code:

public static void Main()
{
    Program.DoSomething<int>();
    Program.DoSomething<object>();
    Program.DoSomething<dynamic>();

    Console.WriteLine("Press any key to continue...");
    Console.ReadKey(true);
}

public static T DoSomething<T>() where T : new()
{
    Console.WriteLine(
        "The type is: {0}; equal to object: {1}.",
        typeof(T).FullName,
        typeof(T) == typeof(object));

    dynamic result = new ExpandoObject();
    result.Hello = "Hello";
    result.Number = 123;

    try
    {
        return (T)result;
    }
    catch (Exception)
    {
        Console.WriteLine("Can't cast dynamic to the generic type.");
        return new T();
    }
}

产生:

类型是:System.Int32;等于对象:False.
无法将动态类型转换为泛型类型.
类型是:System.Object;等于对象:True.
类型是:System.Object;等于对象:True.

The type is: System.Int32; equal to object: False.
Can't cast dynamic to the generic type.
The type is: System.Object; equal to object: True.
The type is: System.Object; equal to object: True.

如何在泛型方法中确定类型参数是动态对象还是普通对象?

How is it possible to determine, within the generic method, whether the type parameter is dynamic or an ordinary object?

推荐答案

否，您不能.动态是情人眼中的一切(意思是:编译器).实现为动态.但是，您可以检查 IDynamicMetaObjectProvider :如果某个对象实现了该功能，则调用方可能正在谈论 dynamic .不幸的是，反射也可以在 dynamic 内部使用，但完全不会涉及 IDynamicMetaObjectProvider .

No, you cannot. Dynamic is all in the eye of the beholder (meaning: the compiler). It is implemented as dynamic. You can, however, check for IDynamicMetaObjectProvider: if an object implements that, the caller is probably talking about dynamic. Unfortunately, reflection also works inside dynamic, but will not involve IDynamicMetaObjectProvider at all.

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