Item 

Description 

CoClass Name  

Specify the class whose properties and methods you want to expose to client applications. (Delphi prepends a T to this name.)  

Instancing  

Specify an instancing mode to indicate how your Automation server is launched.  

Threading Model  

Choose the threading model to indicate how COM serializes calls to your Automation object’s interface. The threading model you choose determines how the object is registered. You must make sure that your object implementation adheres to the model selected.  

Generate Event support code  

Check this box to tell the wizard to implement a separate interface for managing events on your Automation object. The separate interface has the name ICoClassNameEvents, and defines the event handlers that must be implemented by the client. Your application does not implement this interface.  

Instancing 

Meaning 

Internal  

The object can only be created internally. An external application cannot create an instance of the object directly.  

Single Instance  

Allows only a single COM interface for each executable (application), so creating multiple instances results in launching multiple instances of the application.  

Multiple Instance  

Specifies that multiple clients can connect to the application. Any time a client requests the object, a separate instance is created within a single process space. (That is, there can be multiple instances in a single executable.)  

Threading Model 

Meaning 

Single Apartment  

Only one client thread can be serviced at a time. COM serializes all incoming calls to enforce this. Your code needs no thread support.  

Free  

Each object instance may be called by multiple threads simultaneously. You must protect instance data as well as global memory.  

Both  

This is the same as the Free-threaded model, except that all callbacks supplied by clients are guaranteed to execute in the same thread. This means you do not need protect values supplied as parameters to callback functions.  

Neutral  

Multiple clients can call the object on different threads at the same time, but COM ensures that no two calls conflict. You must guard against thread conflicts involving global data and any instance data that is accessed by more than one method. This model should not be used with objects that have a user interface. This model is only available under COM+. Under COM, it is mapped to the Apartment model.