c# - 如何知道类型参数是否是动态的？

Question

似乎每次dynamic被泛型方法的调用者使用时，实际使用的类型都是一个简单的object。例如代码:

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:

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.

如何在泛型方法中判断类型参数是动态的还是普通对象？

Answer 1

不，你不能。动态在旁观者的眼中(意思是:编译器)。它作为动态实现。但是，您可以检查 IDynamicMetaObjectProvider:如果一个对象实现了它，则调用者可能正在谈论 dynamic。不幸的是，反射也在 dynamic 中起作用，但根本不会涉及 IDynamicMetaObjectProvider。