Question

我有一项服务需要将字符串泵送到帮助应用程序，该应用程序显示从服务到用户的关键消息（Vista +不提供对GUI的服务访问）。由于我在TCP上使用了.NET Remoting，我想我会对IPC协议做同样的事情。但是，在获取对远程对象的引用后，在调用远程方法时出现以下异常：

MissingMethodException: No parameterless constructor defined for this object.

简单地在类中添加无参数构造函数会在进行调用时给出NullReferenceException。我做错了什么？我在下面列出了我的相关代码：

申请代码

public class MyMsgBus : MarshalByRefObject, IDisposable, IMxServeBus
{
    private Thread myThread = null;
    private volatile List<string> myMsgBus = null;
    private volatile bool myThreadAlive = false;
    private volatile bool myIsDisposed = false;
    private volatile bool myIsDisposing = false;
    private IpcChannel myIpc = null;

    public MyMsgBus(string busname)
    {
       myMsgBus = new List<string>();

       myIpc = CreateIpcChannel(busname);
       ChannelServices.RegisterChannel(myIpc);

       var entry = new WellKnownServiceTypeEntry(
          typeof(MxServeBus),
          "MyRemoteObj.rem",
          WellKnownObjectMode.Singleton);

       RemotingConfiguration.RegisterWellKnownServiceType(entry);
    }

    // defined in IMyMsgBus
    public void SendMessage(string message)
    {
       // do stuff
    }

    public static IpcChannel CreateIpcChannel(string portName)
    {
       var serverSinkProvider = new BinaryServerFormatterSinkProvider();
       serverSinkProvider.TypeFilterLevel = TypeFilterLevel.Low;

       IDictionary props = new Hashtable();
       props["portName"] = portName;
       props["authorizedGroup"] = "Authenticated Users";

       return new IpcChannel(props, null, serverSinkProvider);
    }

    public static IpcChannel CreateIpcChannelWithUniquePortName()
    {
       return CreateIpcChannel(Guid.NewGuid().ToString());
    }
}

测试客户端

static void Main(string[] args)
{
   var channel = MyMsgBus.CreateIpcChannelWithUniquePortName();
   ChannelServices.RegisterChannel(channel, true);

   var objUri = "ipc://MyMsgBus/MyRemoteObj.rem";
   IMyMsgBus lBus = (IMyMsgBus)Activator.GetObject(typeof(IMyMsgBus), objUri);
   lBus.SendMessage("test");
   Console.WriteLine();
}

提前感谢您提供任何帮助。作为FYI，这是通过使用共享接口配置的远程实例，其中IMyMsgBus定义了可通过IPC调用的方法。

Answer 1

在添加无参数构造函数时，您将获得NullReferenceException，因为正确初始化需要参数。如果不提供它，则会错过初始化的某些部分。

您应该重构代码以允许参数较少的构造函数为

   private bool _initialized = false;

    public MyMsgBus() {}

    public Initialize(string busname) // Make this part of interface    
    {
       myMsgBus = new List<string>();

       myIpc = CreateIpcChannel(busname);
       ChannelServices.RegisterChannel(myIpc);

       var entry = new WellKnownServiceTypeEntry(
          typeof(MxServeBus),
          "MyRemoteObj.rem",
          WellKnownObjectMode.Singleton);

       RemotingConfiguration.RegisterWellKnownServiceType(entry);
       _initialized = true;
    }

在所有其他公共方法中，如果flag为false，请检查_initialized标志和throw NotInitializedException。

您应该将其用作

 IMyMsgBus lBus = (IMyMsgBus)Activator.GetObject(typeof(IMyMsgBus));
 lBus.Initialize(objUri);
 ... do Further operation

在IPC上进行.NET Remoting调用时出现MissingMethodException

1 个答案: