c# - 通过 RealProxy 引用参数

Question

我需要通过 RealProxy 调用带有 ref-arguments 的方法。我已将问题隔离到以下代码：

using System;
using System.Reflection;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Proxies;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
             HelloClass hello=new HelloClass();
             TestProxy proxy = new TestProxy(hello);
             HelloClass hello2 = proxy.GetTransparentProxy() as HelloClass;

             string t = "";
             hello2.SayHello(ref t);
             Console.Out.WriteLine(t);
        }
    }

    public class TestProxy : RealProxy
    {
         HelloClass _hello;

         public TestProxy(HelloClass hello)
             : base(typeof(HelloClass))
         {
             this._hello = hello;
         }

         public override System.Runtime.Remoting.Messaging.IMessage Invoke(System.Runtime.Remoting.Messaging.IMessage msg)
        {
            IMethodCallMessage call = msg as IMethodCallMessage;
            object returnValue = typeof(HelloClass).InvokeMember(call.MethodName, BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, _hello, call.Args);
            return new ReturnMessage(returnValue, null, 0, call.LogicalCallContext, call);
        }
    }

    public class HelloClass : MarshalByRefObject
    {
        public void SayHello(ref string s)
        {
            s = "Hello World!";
        }
    }
}

该程序应生成“Hello World！” 输出，但不知何故，对 ref 参数的修改在代理中丢失了。我该怎么做才能让它工作？

Answer 1

ReturnMessage 的第二个参数需要包含 ref 和 out 参数的值才能传回。您可以通过保存对传入数组的引用来获取它们：

public override System.Runtime.Remoting.Messaging.IMessage Invoke(System.Runtime.Remoting.Messaging.IMessage msg)
{
    IMethodCallMessage call = msg as IMethodCallMessage;
    var args = call.Args;
    object returnValue = typeof(HelloClass).InvokeMember(call.MethodName, BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, _hello, args);
    return new ReturnMessage(returnValue, args, args.Length, call.LogicalCallContext, call);
}