COM/COM+ services and components in .NET, Part- IV

COM/COM+ services and components in .NET

1. Explain transaction
   atomicity. We must ensure that the
   entire transaction is either committed or rolled back.
2. Explain consistency. We must ensure that the
   system is always left at the correct state in case of the failure or
   success of a transaction.
3. Explain integrity. Ensure data integrity by
   protecting concurrent transactions from seeing or being adversely
   affected by each other’s partial and uncommitted results.
4. Explain durability. Make sure that the system can
   return to its original state in case of a failure.
5. Explain object pooling. With object pooling, COM+
   creates objects and keeps them in a pool, where they are ready to be
   used when the next client makes a request. This improves the performance
   of a server application that hosts the objects that are frequently used
   but are expensive to create.
6. Explain JIT activation. The objective of JIT
   activation is to minimize the amount of time for which an object lives
   and consumes resources on the server. With JIT activation, the client
   can hold a reference to an object on the server for a long time, but the
   server creates the object only when the client calls a method on the
   object. After the method call is completed, the object is freed and its
   memory is reclaimed. JIT activation enables applications to scale up as
   the number of users increases.
7. Explain role-based security. In the role-based security
   model, access to parts of an application are granted or denied based on
   the role to which the callers belong. A role defines which members of a
   Windows domain are allowed to work with what components, methods, or
   interfaces.
8. Explain queued components. The queued components service
   enables you to create components that can execute asynchronously or in
   disconnected mode. Queued components ensure availability of a system
   even when one or more sub-systems are temporarily unavailable. Consider
   a scenario where salespeople take their laptop computers to the field
   and enter orders on the go. Because they are in disconnected mode, these
   orders can be queued up in a message queue. When salespeople connect
   back to the network, the orders can be retrieved from the message queue
   and processed by the order processing components on the server.
9. Explain loosely coupled events.
   Loosely coupled events enable
   an object (publisher) to publish an event. Other objects (subscribers)
   can subscribe to an event. COM+ does not require publishers or
   subscribers to know about each other. Therefore, loosely coupled events
   greatly simplify the programming model for distributed applications.
10. Define scalability. The application meets its
    requirement for efficiency even if the number of users increases.
11. Define reliability. The application generates
    correct and consistent information all the time.
12. Define availability. Users can depend on using the
    application when needed.
13. Define security. The application is never
    disrupted or compromised by the efforts of malicious or ignorant users.
14. Define manageability. Deployment and maintenance of
    the application is as efficient and painless as possible.
15. Which namespace do the
    classes, allowing you to support COM functionality, are located? System.EnterpriseServices

How do you make a NET
component talk to a COM component? To enable the communication between COM and .NET
components, the .NET Framework generates a COM Callable Wrapper (CCW).
The CCW enables communication between the calling COM code and the
managed code. It also handles conversion between the data types, as well
as other messages between the COM types and the .NET types.