COM+ Interview Questions & Answers

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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.

A proxy object generated by the common language runtime so
that existing COM applications can use managed classes,
including .NET Framework classes, transparently.

by creating typelibraries & wrapper classes

we acn register the Com+ services using the "regsvcs"
command

ContextUtil is the preferred class to use for obtaining
COM+ context information.

1) Automatic Transaction
2) Distributed Transactions
3) Object Pooling

com architecture needs registratation & classids where as .net
architecture does not need registration & classids

Wrapper classes are used to encapsulate values of primitive
types in objects, so that they can be passed around in the
same manner.

Com Callable Wrapper
1)Create Assembly and compile with strong name.
2)Register Assembly using regasm <assembly name>
3)Register Assembly in GAC using gacutil /i <assembly name>
4)Use tlbexp <assemblyname.dll> to export Assembly as Type
Library for COM.

Runtime Callable Wrapper
1)Create Public Key Token file using sn.exe –k
<keyfilename.snk>
2)Use tlbimp <TypeLibFileName> /keyfile: <keyfilename.snk>
/out: <AssemblyName.dll>
3)Register Imported Assembly in GAC using gacutil /i
<AssemblyName.dll>

1. Does not supports implement-inheritence
2. Version compatibility.
3. Fully dependant on registry hence doesn't work on non-window platforms.,

yes because when server transfer data that will in serialize
and any format they used which serialized data in com

We can pass command line arguements in VB. We can
specify the arguement in project properties -> make tab.
Instead we can pass it as command line arguement. The
argument will be in a object called 'command' and/or 'command$'.

8085 is basic microprocessor, why we are learning in 21th
centuri for example: u want lean java , before must know
some C&C++ concepts, other wise it will difficult
like that we learn some basic after will go for advanced

You can no longer install COM+ DLLs into the System32 folder
on the server. In Windows 2003 server and beyond (including
Windows 7) when exporting COM+ package any DLLs registered
in Windows\System32 (or folders below that) will not be
exported. According to Microsoft Support, this is by design.
(This information has not been published publicly by
Microsoft, so we had to open a ticket with them to discover
the issue.)

The symptoms are that the exported MSI files do not contain
the COM+ DLLs if:
1. the COM+ DLL is registered in System32 and
2. the COM+ package is exported on Windows 2003 or later.
The MSI will be created and will install, however the
applications will not be able to instantiate the objects
because the DLL was never installed. Opening the MSI with a
install editor like Wise Installation Editor will reveal
that the DLL is not included in the MSI.

Transaction Atomicity has four attributes:-ACID (atomicity,
consistency, isolation, and durability) is an acronym
device for learning and remembering the four primary
attributes ensured to any transaction by a transaction
manager (which is also called a transaction monitor). These
attributes are given below:
Atomicity. In a transaction involving two or more discrete
pieces of information, either all of the pieces are
committed or none are.

Consistency. A transaction either creates a new and valid
state of data, or, if any failure occurs, returns all data
to its state before the transaction was started.

Isolation. A transaction in process and not yet committed
must remain isolated from any other transaction.

Durability. Committed data is saved by the system such
that, even in the event of a failure and system restart,
the data is available in its correct state.

We must ensure that the system is always left at the
correct state in case of the failure or success of a
transaction.

Ensure data integrity by protecting concurrent transactions
from seeing or being adversely affected by each other?s
partial and uncommitted results.

Make sure that the system can return to its original state
in case of a failure.

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.

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.

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

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.

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.

The application generates correct and consistent
information all the time.

The application meets its requirement for efficiency even
if the number of users increases.