What is marshalling and types of marshalling?

The Marshaling is used when an object is converted so that it can be sent across the network or across the application domains. The Unmarshaling generates an object from the marshaled data. There are 2 ways to do the marshalling:-

1) Marshal-by-value (MBV) :- In this type of marshalling the object is serialized into the channel, and a copy of the object is generated on the other side of the network. The object which is to marshal is stored into the stream, and the stream is used to build a copy of the object on the another side with the unmarshalling sequence.

2) Marshaling-by-reference (MBR):- Here it creates a proxy on the client which  is used to communicate with the remote object. The marshaling sequence of a remote object creates an ObjRef instance which itself can be serialized across the network.

The Objects that are derived from "MarshalByRefObject" are always marshaled by the reference.

To marshal a remote object the static method RemotingServices.Marshal() is used.RemotingServices.Marshal() has following overloaded versions:-

public static ObjRef Marshal(MarshalByRefObject obj)

 public static ObjRef Marshal(MarshalByRefObject obj, string objUri)

 public static ObjRef Marshal(MarshalByRefObject obj, string objUri,Type requestedType)

The very First argument obj specifies the object to marshal. The objUri is the path which is stored within the marshaled object reference; it can be used to access the remote object. The requestedType is used to pass a different type of the object to the object reference. This is very useful if the client using the remote object shouldn't use the object class but an interface that the remote object class implements instead. In this scenario the interface is the requestedType which must be used for the marshaling.