Visual Basic Interview Questions and Answers

Visual Basic Interview Questions and Answers

How do you register a component?

Compiling the component, running REGSVR32 MyDLL.dll

Name and explain the different compatibility types when creating a COM component 

No Compatibility ? New GUID created, references from other components will not workProject Compatibility ? Default for a new component 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 can not modify the same code at the same time.

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

SetComplete and SetAbort. 

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

DCOMCONFIG.EXE

What does Option Explicit refer to? 

All variables must be declared before use. Their type is not required.

What are the different ways to Declare and Instantiate an object in Visual Basic 6?

Dim obj as OBJ.CLASS with eitherSet obj = New OBJ.CLASS orSet obj = CreateObject(OBJ.CLASS?) orSet obj = GetObject( , OBJ.CLASS?)orDim obj as New OBJ.CLASS

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

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 detectedDynamic ? All changes are visible.

Name the four different locking type in ADO and describe them briefly. 

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 )? 

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 are the ADO objects? 

Provide a scenario using three of them to return data from a database. Expected answer: Connection Connects to a data source; contains the Errors collectionCommand Executes commands to the data source. Is the only object that can accept parameters for a stored procedure.Recordset The set of data returned from the database.Scenario: There are many possibilities. The most likely is as follows:Dim conn As ADODB.ConnectionDim rs As ADODB.RecordsetDim Cmd As ADODB.Commandconn.ConnectionString = ?CONNECTION STRING?conn.OpenSet Cmd.ActiveConnection = connCmd.CommandText = ?SQL STATEMENT?Set rs = Cmd.ExecuteSet rs.ActiveConnection = Nothingconn.Close

Under the ADO Command Object, what collection is responsible for input to stored procedures? 

The Parameters collection.

What are some benefits of using MTS?

Database Pooling, Transactional operations, Deployment, Security, Remote Execution.

What is the benefit 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.

Describe and In Process vs. Out of Process component. Which is faster? 

An in-process component is implemented as a DLL, and runs in the same process space as its client app, enabling the most efficient communication between client and component.Each client app that uses the component starts a new instance of it.An out of process component is implemented as an EXE, and unlike a dll, runs in its own process space. As a result, exe’s are slower then dll’s because communications between client and component must be marshalled across process boundaries. A single instance of an out of process component can service many clients.

What are the main components of the ADO object model? How are they used?

 
Connection: Used to make a connection between your app and an external data source, ie, sql server.Command: Used to build queries, including user-specific parameters, to access records from a data source (which are returned in a Recordset)Recordset:Used to access records returned from an SQL query. With a recordset, you can navigate returned records. You can also add, modify or delete records.

Can We create CGI scripts in VB?? 

Yes.

Dim x, y as integer. What is x and y data type? 

X as variant and y as integer.

What is Centralization Error Handling? 

Writing function and calling it when error occurs.

What is frx? 

When some controls like grid and third party control placed in our application then it will create frx in run time.

What is the Dll required for running the VB? 

Vbrun300.dll

Why we use Treeview Control? 

To list the hierarchical list of the node objects. Such of files and Directories.

Handling Error in Calling chain. 

This will call the top most error where the error is handled.

In project properties if we set Unattended what is it mean? 

This cannot have user interface. This can be used for the COM creation.

What is the size of the variant data type? 

The Variant data type has a numeric storage size of 16 bytes and can contain data up to the range of a Decimal, or a character storage size of 22 bytes (plus string length),and can store any character text.

What is view Port?

The area under which the container provides the view of the ActiveX Document is known as a view port. 

What are the different types of error? 

Syntax Errors, Runtime , Logic.

What is the diff between the Std and Class Module? 

Std Global with in the project. Cls Global through out the all project only thing is we want to set the type lib. Class Modules can be Instantiated.

What is Mixed Cursors? 

Static + Keyset

Drag and Drop state numbers and functions? 

State 0 Source control is being dragged with the range of a target.
1 Out of the range of a target.
2 One position in the target to another.

What are the Style Properties of Combo Box? 

Simple, Dropdown list We can type and select. Dropdown Combo Only Drop Down.

What are the Style properties of List Box? 

Simple Single Select , Extended. Multiple Select.

What is Collection Objects? 

Similarly to arrays but is preferred over an array because of the following reasons.
1. A collection objects uses less Memory than an array.
2. It provides methods to add and delete members.
3. It does not required reason statement when objects are added or deleted.
4. It does not have boundary limitations.

What is the difference between Property Get, Set and Let? 

Set Value is assigned to ActiveX Object from the form.
Let Value is retried to ActiveX Object from the form.
Get- Assigns the value of an expression to a variable or property.

How to change the Mouse Pointer? 

Screen.MousePointer = VBHourGlass/VBNormal.