1. Copyright © 2003, developerLabs Extending.NET Distributed Applications Stephen Fulcher developerLabs

2. Copyright © 2003, developerLabs Topics General Extensibility Remoting Extensibility

3. Copyright © 2003, developerLabs General Extensibility Custom configuration  The.NET configuration hierarchy can be extended arbitrarily  New configuration sections can be defined and we can supply handlers for those sections Programmatic type activation  Configuration metadata can be used to describe types to the satisfaction of the loader  Assembly loading might be required  Types activated in this manner must already be compiled into assembly form Programmatic type generation  The CodeDOM namespace includes support for programmatically generating and compiling types  The reflection namespace also includes a technique for creating a type programmatically

4. Copyright © 2003, developerLabs Remoting Extensibility - Overview Crossing a context, application domain, process or machine boundary requires marshaling Objects can be marshaled by value of by reference MBROs can be activated by the server or the client  Server activated objects include single-call and singleton Object life-cycle varies by activation type  Singletons use a lease-based lifecycle  Client activated objects use a lease-based lifecycle  Single-call objects live through a single call

5. Copyright © 2003, developerLabs Infrastructure Object activation requests return an ObjRef instance The ObjRef is unpacked/unmarshaled into a transparent proxy  The transparent proxy leverages unmanaged memory to model the server side object  A transparent proxy holds a reference to a real proxy

6. Copyright © 2003, developerLabs Infrastructure The RealProxy type is abstract, and has a RemotingProxy implementation The RealProxy type instances take the unmanaged memory block managed by the transparent proxy and turn it into a Message Messages implement the IMessage interface and basically encapsulate a collection of key- value pairs, an IDictionary reference

7. Copyright © 2003, developerLabs Infrastructure The message is passed from the real proxy to the envoy sink chain A sink object can operate on the message as part of a chain Each sink object implements the IMessageSink interface:  NextSink  AsyncProcessMessage  SyncProcessMessage An envoy sink operates in the context of the client holding the reference to the transparent proxy The envoy sink chain has a terminator sink at the end that passes off to the client context sink chain

8. Copyright © 2003, developerLabs Infrastructure The message is passed from the real proxy to the context sink chain Each context sink in the chain gets to operates on a message The last sink in the context chain is the terminator context sink  If the call is simply a cross-context call, the terminator sink passes the message to the cross-context channel, a lightweight channel  If the call target is in a different application domain, process or machine, the terminator sink passes the message out of the client object context to the channel sink chain The channel sink chain prepares the message for transport to the remote process/machine

9. Copyright © 2003, developerLabs Infrastructure The first sink in the channel sink chain is the formatter, which implements IFormatter This sink serializes the message to the initial wire format The platform includes two formatters, SoapFormatter and BinaryFormatter The message is passed fro the formatter sink to a set of channel sinks These channel sinks can operate on the serialized message format before transport The terminator channel sink is the transport sink, which passes the message off to transport

10. Copyright © 2003, developerLabs Infrastructure On the server side, a reasonably symmetric set of sink chains exist going from the transport wire to the remote object The transport sink passes to the channel sink chain, which passes to the server context sink chain, which passes to the server object sink chain The last sink is the Stackbuilder sink, which preps the stack for the call to the remote object After the call, the server object sinks take the result from the call, pack it into a message, and send it back through the infrastructure to the client

11. Copyright © 2003, developerLabs Extensibility Points Custom ObjRef types Custom proxies  These are classes that derive from RealProxy and replace RemotingProxy  These work for client-side only logic in contrast with something that has part on the client and a part on the server, like encryption/decryption

12. Copyright © 2003, developerLabs Extensibility Points Custom message types: IMessage  In particular, message headers Custom message sinks: IMessageSink  Envoy sinks  Context sinks

13. Copyright © 2003, developerLabs Extensibility Points Custom channel sinks  Formatter sink: IFormatter  Channel sink: BaseChannelSinkWithProperties, IXXXChannelSink

14. Copyright © 2003, developerLabs Resources Books  Advanced.NET Remoting, APress  Microsoft.NET Remoting, MSPress Free stuff  SDK docs  http://www.ingorammer.com http://www.ingorammer.com  http://www.gotdotnet.com http://www.gotdotnet.com  http://msdn.microsoft.com http://msdn.microsoft.com