客户端对象（代理）如何注册要在服务器端触发的事件？

Question

I would like to make a class where the client side (proxy) of the instantiated object can register to an event (or delegate) and be informed whenever this event is fired on the server side.

I tried directly but I get a SecurityException informing me that System.DelegateSerializationHolder cannot be serialized at this security level.

Is there a way around this?

Example:

MyClass proxy = Activator.GetObject(typeof(MyClass ), uri) as MyClass;
proxy.OnMyEvent += new MyEventHandler(this.Callback);

Answer 1

No. Not directly anyway.

Your choices would be to either have the client call back to the server and register a with it a port for out of band controls from the server. This could open up all sorts of security concerns.

Probably the best way would be to have the client poll the server to see if any events need to be processed. This leaves the control of information requests in the clients domain, and is how Microsoft Exchange and other products I've worked with tend to handle this scenario.

Answer 2

Yes, it is possible, but it's deactivated by default.

The default .net Remoting deserialization level is Low , which does not allow Delegates to be passed over the Remoting boundary. You can create a custom BinaryServerFormatterSinkProvider with a deserialization level of Full and pass this provider to your channel (on the server side).

Here's a VB.NET example; see the MSDN article on Automatic Deserialization in .NET Framework Remoting for a C# example.

Dim myChannel = New TcpServerChannel("", myPort, _
                                     New BinaryServerFormatterSinkProvider() With {.TypeFilterLevel = Runtime.Serialization.Formatters.TypeFilterLevel.Full})