COM+ Threading Models
The following are the four most common types of COM+ threading models:
The Single-Threaded Server
Most COM+ servers to date have been developed using the single-threaded server threading model. In this model, all method calls to all objects are done by the same thread. The single thread has one apartment where out-of-process calls to the COM+ server are serialized. Each out-of-process COM+ call is placed on the apartment's message queue. Calls on the message queue are processed one at a time by the apartment thread. This threading model completely eliminates any concurrency problems involving either per-object data or shared data.
The apartments in this model ...