(Interview) Visual Basic Interview Questions (Page-2)

Interview : Visual Basic Interview Questions

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("Do you do this?" followed by "Okay, do it then"), late binding is much less efficient than early binding. Except where early binding is not supported (ASP, scripting, etc.), late binding should only be used in very special cases.

It is a common misconception that any code using the CreateObject function instead of Set = New is using late binding. This is not the case. The type declaration of the object variable determines whether
it is late or early bound, as in the following:

Dim A As Foo
Dim B As Foo
Dim C As Object
Dim D As Object

Set A = New Foo 'Early Bound
Set B = CreateObject("FooLib.Foo") 'Early Bound
Set C = CreateObject("FooLib.Foo") 'Late Bound
Set D = New Foo 'Late Bound
What are the Advantages of disconnected recordsets?

A disconnected Recordset, as its name implies, is a Recordset that lacks a connection.

seen that a Recordset that does not have a database connection can be very useful as a tool in your programming. It can save you time and effort and make your code more scalable.

In order to create a disconnected Recordset two Recordset properties must be set appropriately.
It is a requirement that the CursorLocation property is set to adUseClient and the LockType property is set to adLockBatchOptimistic. Note that the CursorType will default to adUseStatic if we don't explicitly state that it should be set to adUseClient.) i.e

rst.LockType = adLockBatchOptimistic
rst.CursorLocation = adUseClient

However, we've recently discovered that these steps aren't necessary. VB automatically assigns batch optimistic locking to newly created,
connectionless recordsets. And, of course, without a connection, a recordset can't have any other cursor but a client-side one. To create one of these structures, then, the only thing you need do is create
the object variable instance. After that, you can simply begin adding fields to the construct.

To add fields, you use the Fields collection's Append method. This method requires two parameters , the field name and the field data type. So, to create a connectionless recordset with two fields,you'd use code similar to:

Dim rst As ADODB.Recordset
Set rst = New ADODB.Recordset

rst.Fields.Append "CustID", adVarChar
rst.Fields.Append "CustName", adVarChar

Additional, optional Append method parameters include DefinedSize and Attrib. The DefinedSize argument takes the size of the field. Fill the Attrib parameter with constants that define additional field characteristics, such as whether it will allow null values or is updatable.
Since, in our technique, we want the fields to mirror the structure of the original recordset, we'll simply use existing values for these parameters.

Disconnected Recordsets, first available with ADO 2.0, are the most commonly used mechanism to retrieve a Recordset and open a connection for only the necessary amount of time, thus increasing scalability. They are call disconnected because the connection to the database is closed.
The collections, properties, and methods of a disconnected Recordset are still available even though the connection is closed. This frees up server resources, given that the number of open connections is limited and database locking is a non-issue.
What are Benefits of wrapping database calls into MTS transactions?

If database calls are made within the context of a transaction, aborting the transaction will undo and changes that occur within that transaction.
This removes the possibility of stranded, or partial data. Transaction that uses the Microsoft? Transaction Server (MTS) environment. MSMQ implicitly uses the current MTS transaction if one is available.

BENIFTIS OF USING MTS :
Database Pooling, Transactional operations, Deployment, Security, Remote Execution 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.


How to register a component?

Compiling the component, running REGSVR32 MyDLL.dll
Controls which do not have events ?

Shape and line controls are useful for drawing graphical elements on
the surface of a form. These controls don't support any events; they
are strictly for decorative purposes.

EXTRA INFO::
The image, shape and line controls are considered to be lightweight controls; that is, they support only a subset of the properties, methods, and events found in the picture box. Because of this, they typically require less system resources and load faster than the picture box control.


What are the Control Categories?

a)Intrinsic controls:
such as the command button and frame controls. These controls are contained inside the Visual Basic .exe file. Intrinsic controls are always included in the toolbox

b)ActiveX controls:
which exist as separate files with a .ocx file name extension. These include controls that are available in all editions of Visual Basic (DataCombo, DataList controls, and so on) and those that are available only in the Professional and Enterprise editions (such as Listview, Toolbar, Animation, and Tabbed Dialog). Many third-party ActiveX controls are also available.

c)Insertable Objects:
such as a Microsoft Excel Worksheet object containing a list of all your company's employees, or a Microsoft Project Calendar object containing the scheduling information for a project. Since these can
be added to the toolbox, they can be considered controls.Some of these objects also support Automation (formerly called OLE Automation),which allows you to program another application's objects from within a Visual Basic application.
DIFF between Image and Picture box controls?

The sizing behavior of the image control differs from that of the picture box. It has a Stretch property while the picture box has an AutoSize property. Setting the AutoSize property to True causes a picture box to resize to the dimensions of the picture; setting it to False causes the picture to be cropped (only a portion of the picture is visible). When set to False (the default) , the Stretch property of the image control causes it to resize to the dimensions of the picture.
Setting the Stretch property to True causes the picture to resize to the size of the image control, which may cause the picture to appear
distorted.


Default property of datacontrol ?...

Connect property......

Define the scope of Public, Private, Friend procedures?

The set of public variables, methods, properties, and events described in a class module define the interface for an object. The interface consists of the object members that are available to a programmer who's using the object from code.

You can create private variables, methods, properties, and events that are used by other procedures within the class module but are not part of the object's public interface. Additionally, constants user-defined types, and Declare statements within a class module must always be private.

The Friend keyword makes a procedure private to the project: The procedure is available to any code running within the project, but it is not available to a referencing project.

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