Programming .NET Components, 2nd Edition

Marshaling-by-Reference Activation Modes

.NET supports two kinds of marshal-by-reference objects: client-activated and server- activated. The two kinds map to three activation modes : client-activated object, server-activated single-call, and server-activated singleton. The different activation modes control object state management, object sharing, the object lifecycle, and the way in which the client binds to an object. The client decides whether to use client-activated or server-activated objects. If the client chooses client-activated objects , just one activation mode is available. If the client chooses server-activated objects, it’s up to the hosting app domain to decide whether the client will get a server-activated single-call object or a server-activated singleton object. These objects are called server-activated because it’s up to the host to activate the object on behalf of the client and bind it to the client. The hosting app domain indicates to .NET which activation modes it supports, using server registration. The host can support both client- and server-activated objects, or just one of these types; it’s completely at the discretion of the host. If it decides to support a server-activated mode, the host must register its objects either as single-call objects or as singleton objects, but not both. This will all become clearer later in this chapter, when you see the actual registration code. The next sections explain the different activation modes.

Client-Activated Object ...