Interview Questions.

Question 1. What Is In-proc?

Answer :

In-proc server is a COM element, whilst example is the server is loaded into the caller technique area. In-Proc  server may be effortlessly recognized by way of .Dll extension.

Out-of-Proc server is a COM element that run in its personal  procedure area and for any times created via the customers, a proxy is created inside the users system space. Proxy is responsible for interacting with the server to perform  operation on behalf of the customer. (.Exe extension).

Question 2. Suppose We Have Object B And Aggregated Object C (in- Proc Server), Created By B. Can You Access Any Interface Of B From C? What's The Difference Between Aggregated And Contained Objects?

Answer :

For the first query, Yes, we are able to since the QueryInterface () policies of thumb suggest that if we are able to query an interface  of C from B, we must be capable of query the viceversa.The IUnknown implementation of both the items has to do the 'magic'.

For the second one query, Aggregation bounds outer and internal  gadgets collectively and gives the user the interface suggestions  of either gadgets to get admission to it at once in order that the person  never knows the objects are aggregated. 

But while containment is used, the interface of internal item  never exposed to the client immediately alternatively the outer  object receives the calls and forwards internally. Here  also, the user does not understand the gadgets are contained.

Web Services Interview Questions
Question 3. What Is A Moniker?

Answer :

An item that implements the IMoniker interface. A moniker  acts as a call that uniquely identifies a COM object. In the equal manner that a route identifies a document within the file  device, a moniker identifies a COM object within the directory  namespace.

Question four. What Is The Difference, If Any, Between Ole And Com?

Answer :

OLE is a set of technologies to aid linking and  embedding. COM lies in OLE as one of the technology. COM  defines a binary wellknown / set of policies for growing  reusable components.

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Question 5. How To Create An Instance Of The Object In Com?

Answer :

To create the instance of COM componet use the subsequent 

WIN32 APIs

To get entry to the element that became there in local system use  following API

CoCreateInstance(clsid,NULL(used for 

aggregation),CLSCTX_ALL,Interface_GUID,(void**)

&pRequestedInterface );

To get right of entry to the COM componet remotely use the subsequent API

CoCreateInstanceEx

(CLSID,NULL,CLSCTX_ALL,COSERVERINFO,Interface_GUID,MULTI_QI*

);

Java Script Interview Questions
Question 6. What Happens When Client Calls Cocreateinstance?

Answer :

Reads RootClassesProgId for the matching ProgID
Reads RootClassesProgId for the matching CLSID. The CLSID is examine from the above step.
From the CLSID key, the server kind and photograph filename is thought.
Depending upon the server kind, it starts offevolved the server.
Calls CoGetClassObject feature to get a cope with to the manufacturing facility item.
Then calls createinstance on the manufacturing unit interface to get the pointer to the derived item.
Question 7. What Should Queryinterface Functions Do If Requested Object Was Not Found?

Answer :

Returns a pointer to the modern interface if a hit or 

E_NOINTERFACE in any other case.

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Question 8. What Is Iunknown? What Methods Are Provided By Iunknown?

Answer :

IUnknown is a form of COM Interface.

Every COM magnificence implements an interface named IUnKnown.

IUnKnown incorporates three techniques:

HRESULT QueryInterface()
ULONG AddRef()
ULONG Release()
Question 9. What Are The Purposes Of Addref, Release And Queryinterface Functions?

Answer :

Query Interface approach is used to get the pointer to the interface laid out in one of the parameters of this  technique. Client then makes use of this pointer to call the approach of the issue. 

AddRef and Release are used to boom and decrease the  rely of the example of aspect loaded in memory  respectively. When the count reaches 0 the factor is unloaded.

ActiveX Interview Questions
Question 10. Which Tool Is Used To Configure The Port Range And Protocols For Dcom Communications?

Answer :

use DCOMCONFIG.EXE

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Question 11. Can A Com Interface Be Implemented By More Than One Com Class In The Same Com Component?

Answer :

NO.

OOPS Interview Questions
Question 12. How Do You Know It Is General Dll Or Com Dll?

Answer :

Open the dll in dependency walker software(depends.Exe).

If the dll is having following capabilities:

DLLRegisterServer
DLLUnRegisterServer
DLLCanUnloadNow
DLLGetClassObject
It is a COM DLL in any other case it isn't always.

Web Services Interview Questions
Question thirteen. Explain Futures Of Com?

Answer :

Defines a binary general for element interoperability 
Is programming language-unbiased 
Is provided on multiple platforms (Microsoft® Windows®, 
Microsoft Windows NT™, Apple® Macintosh®, UNIX®) 
Provides for sturdy evolution of issue-based programs and structures 
Is extensible
Windows Communication Foundation (WCF) Tutorial
Question 14. When You Call Co Initialize(null) Function How It Works Internally?

Answer :

CoInitialize will initialize the COM library and will circulate the executing thread to a STA or Single Threaded Apartment Apartment is the logical entity in which threads stay.

Question 15. Differentiate Normal Dll To Com Dll?

Answer :

COM Dll exposes Interface on the opposite to regular DLL  that exports features. Clients create the pointer to  COMDLL's interface to name the methods defined through the factor that implements the interface. 

That outcomes in isolation of implementation and definition  of method inside the interface. Client doesnt need to relink or  recompile the code if approach within the com dll adjustments as a ways as the definition of the interface remains identical.

Windows Communication Foundation (WCF) Interview Questions
Question 16. Define And Explain About Com?

Answer :

COM (Component Object Model) era within the Microsoft  Windows-circle of relatives of Operating Systems enables software program additives to communicate. COM is used by developers to create re-usable software components, link components  collectively to construct applications, and take advantage of Windows services.

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Question 17. How To Call A Dll As A Com Dll?

Answer :

In order to name your DLL as COM dll, you have to observe  some policies to broaden the dll. If those regulations are there  then only your DLL will be referred to as as COM dll.

COM is a specification set of regulations to broaden binaries, COM isn't always a language.

Java XML Interview Questions
Question 18. Do Com Keep Track Of All The Object References (accounting)?

Answer :

Object references in COM is accounted the usage of two methods of IUnknown Interface (AddRef and Release).

AddRef: Increments a reference count whereas "Release" decrements the count. When the count of the reference is zero the DLL is unloaded  from memory.

Java Script Interview Questions
Question 19. What Are The Different Compatibility Types When We Create A Com Component?

Answer :

No Compatibility
Project Compatibility
Binary Compatibility
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Question 20. What Kind Of Components Can Be Used As Dcom Servers?

Answer :

There are  type additives:

1. InProc

2. OutProc

We can use each as DCOM servers, its upto our layout.

COM+ Interview Questions
Question 21. How Does A Dcom Component Know Where To Instantiate Itself?

Answer :

While gaining access to the DCOM issue you have to provide COSERVERINFO shape. This structure is having the statistics about wherein the aspect is.

Question 22. C Is Aggregated By B, Which In Turn Aggregated By A. Our Client Requested C. What Will Happen?

Answer :

QueryInterface to A will delegate request to B which, in  turn, will delegate request for the interface to C. This pointer might be lower back to the patron.

Question 23. What Are Queued Components?

Answer :

Queued Components, a key function of COM+ and based on  Microsoft Message Queuing Services (MSMQ), offers an easy  way to invoke and execute additives asynchronous. Processing can arise with out regard to the provision or accessibility of both the sender or receiver. A domestic  purchasing community is an instance of the form of utility  that might gain from asynchronous processing. In this  asynchronous, disconnected state of affairs where visitors smartphone in  to numerous operators, orders are taken en masse and are  then queued for later retrieval and processing via the  server.

JSON (JavaScript Object Notation) Interview Questions
Question 24. How Do You Make A Net Component Talk To A Com Component?

Answer :

RCW is used for creating a NET compnent communicate to a com thing. CCW is used for Com to .NET conversation.

UMTS Interview Questions