c# - 如何使用即兴接口(interface)访问代理对象

Question

使用 impromptu-interface 时如何访问 Duck Typed 代理对象.考虑我的示例代码，当我尝试将我的 Duck Typed Object 转换为代理对象时，我得到一个 InvalidCastException:

using System;
using ImpromptuInterface;

namespace ConsoleApplication1
{
    public class Duck
    {
        public string Says { get; set; }

        public int GetNumberOfQuacksPerMinute()
        {
            return 42;
        }
    }

    public interface IPondBird
    {
        string Says { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            // Duck says Quack! Quack!! Quack!!!
            var thing = new Duck { Says = "Quack! Quack!! Quack!!!" };

            IPondBird myInterface = Impromptu.ActLike(thing);

            // ...

            // Later on, I want to get access to a proxied object, but I 
            // get a InvalidCastException here
            Duck proxiedObject = (Duck) myInterface;
            Console.WriteLine("Duck # quacks per minute: " 
                + proxiedObject.GetNumberOfQuacksPerMinute());
        }
    }
}

异常情况如下:

An unhandled exception of type 'System.InvalidCastException' occurred in ConsoleApplication1.exe

Additional information: Unable to cast object of type 'ActLike_IPondBird_c7dd53902ec74f01a3844d4789244ea3' to type 'ConsoleApplication1.Duck'.

Answer 1

你不能。你可以考虑行

IPondBird myInterface = Impromptu.ActLike(thing);

好像是

public class Wrapper : IPondBird 
{
  public Wrapper(Duck duck) { ... }
}
IPondBird myInterface = new Wrapper(thing);

话虽如此，您可以将对 native 对象的引用作为契约(Contract)本身的一部分——例如:

public interface IPondBird
{
    string Says { get; set; }
    object NativeObject { get; }
}

public class Duck
{
    public string Says { get; set; }

    public int GetNumberOfQuacksPerMinute()
    {
        return 42;
    }

    public object NativeObject { get { return this; } }
}

IPondBird myInterface = Impromptu.ActLike(thing);   
var duck = (Duck)myInterface.NativeObject;