(Interview) Visual Basic Interview Questions (Page-5)

Interview : Visual Basic Interview Questions

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What type of multi-threading does VB6 implement?

Apartment model threading


How to register a component?

Compiling the component, running REGSVR32 MyDLL.dll
What is Database Connection pooling (relative to MTS)

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.


What is the tool used to configure the port range and protocols for DCOM communications?
DCOMCONFIG.EXE


What is a Type Library and what is it's purpose ?
The type library may represent another Visual Basic project, or any other executable component that exposes a type library.
Visual Basic creates type library information for the classes you create, provides type libraries for the objects it includes, and lets you access the type libraries provided by other applications.

What are binary and project compatibility?
Visual Basic?s Version Compatibility feature is a way of enhancing your components while maintaining backward compatibility with programs that were compiled using earlier versions. The Version Compatibility box, located on the Component tab of the Project Properties dialog box, contains three options:
No Compatibility:
Each time you compile the component, new type library information is generated, including new class IDs and new interface IDs. There is no relation between versions of a component, and programs compiled to use one version cannot use subsequent versions.

Project Compatibility:
Each time you compile the component the type library identifier is kept, so that your test projects can maintain their references to the component project. All class IDs from the previous version are maintained; interface IDs are changed only for classes that are no longer binary-compatible with their earlier counterparts. Note This is a change in Project Compatibility from Visual Basic 5.0, where all class IDs and interface IDs in the project changed if any one class was no longer binary-compatible.

Important For the purpose of releasing compatible versions of a component, Project Compatibility is the same as No Compatibility.

Binary Compatibility:
When you compile the project, if any binary-incompatible changes are detected you will be presented with a warning dialog. If you choose to accept the warning, the component will retain the type library identifier and the class IDs. Interface IDs are changed only for classes that are no longer binary-compatible. This is the same behavior as Project Compatibility.
If, however, you choose to ignore the warning, the component will also maintain the interface IDs. This option is only available when the compiler determines that the change was in the procedure ID or signature of a method.

Note:: When people talk about Version Compatibility, they?re usually referring to Binary Compatibility.


How to set a shortcut key for label?

object.KeyLabel(keycode) [= string]
You would probably create the menu item as follows:
.Add "keyFile", , , "E&xit", , vbAltMask + vbCtrlMask, vbKeyEnd
The default key label for vbKeyEnd is "End". Thus, the shortcut string will be created by default as "Ctrl+Alt+End".

Name the four different cursor and locking types in ADO and describe them briefly ?

CURSORS::
*********
The cursor types are listed from least to most resource intensive.
Forward Only - Fastest, can only move forward in recordset
Static - Can move to any record in the recordset. Data is static and never changes.
KeySet - Changes are detectable, records that are deleted by other users are unavailable, and records created by other users are not detected Dynamic - All changes are visible.

LOCKING TYPES::
****************
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. Cannot alter the data.


Name the different compatibility types when creating a COM component.

No Compatibility - New GUID (Globally Unique Identifier) created, references from other components will not work Project 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 is it important to use source control software for source code?
Modification history. Code ownership: Multiple people cannot modify the same code at the same time.

List the ADO objects?
Connection - Connects to a data source; contains the Errors collection
Command - Executes commands to the data source. The only object that can accept parameters for a stored procedure Recordset - The set of data returned from the database.
Under the ADO Command Object, The Parameters collection. collection is responsible for input to stored procedures?

What two methods are called from the ObjectContext object to inform MTS that the transaction was successful or unsuccessful?
SetComplete and SetAbort.


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