VB Interview Questions
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Visual Basic Interview Questions
- How do you register a component? Expected answer: Compiling the component, running REGSVR32 MyDLL.dll
- Name and explain the different compatibility types when creating a COM component. Expected answer: No Compatibility ? New GUID created, references from other components will not workProject Compatibility ? Default for a new component <Not as critical to mention this one>Binary Compatibility ? GUID does not change, references from other components will work
- Why iss it important to use source control software for source code? Expected answer: Modification history.Code ownership: Multiple people can not modify the same code at the same time.
Visual Basic Interview Questions II
- Name the four different locking type in ADO and describe them briefly. Expected answer: LockPessimistic ? Locks the row once after any edits occur.LockOptimistic ? Locks the row only when Update is called.LockBatchOptimistic ? Allows Batch Updates.LockReadOnly ? Read only. Can not alter the data.
- Describe Database Connection pooling (relative to MTS ) Expected answer: This allows MTS to reuse database connections. Database connections are put to ?sleep? as opposed to being created and destroyed and are activated upon request.
COM Interview Questions
- What is IUnknown? What methods are provided by IUnknown? It is a generally good idea to have an answer for this question if you claim you know COM in your resume. Otherwise, you may consider your interview failed at this point. IUnknown is the base interface of COM. All other interfaces must derive directly or indirectly from IUnknown. There are three methods in that interface: AddRef, Release and QueryInterface.
- What are the purposes of AddRef, Release and QueryInterface functions? AddRef increments reference count of the object, Release decrements reference counter of the object and QueryInterface obtains a pointer to the requested interface.
COM Interview Questions II
- What’s the difference between COM and DCOM? Again, the question does not require strict answer. Any DCOM object is yet a COM object (DCOM extends COM) and any COM object may participate in DCOM transactions. DCOM introduced several improvements/optimizations for distributed environment, such as MULTI_QI (multiple QueryInterface()), security contexts etc. DCOM demonstrated importance of surrogate process (you cannot run in-proc server on a remote machine. You need a surrogate process to do that.) DCOM introduced a load balancing.
COM Interview Questions III
- How can you guarantee that only remote server is ever created by a client? Create an object (call CoCreateObjectEx()) with CLSCTX_REMOTE_SERVER flag.
- What is __declspec(novtable)? Why would you need this? __declspec(novtable) is a Microsoft’s compiler optimization. The main idea of this optimization is to strip the vtable initialization code from abstract class (for abstract class the vtable is empty, while it is initialized in contructor) MSDN has an article on this topic.
- What is an IDL? IDL stands for Interface Definition Language. IDL is the language to describe COM interfaces.
