VB 6 interview questions includes, using controls, activex, object oriented programming (OOP) concept, in-process and out-process server, creating and using dlls, user controls, data access technology like Data Access Object (DAO), Activex Data Object (ADO), Setup and deployment, registering component, using data reports, Windows application programming interface (WIN API). 

Interview Question, Answer<p1.  Programming General</p2.  Web General3.  Database General4.  Visual Basic 65.  ASP6.  Visual Basic .NET and C#7.  ASP .NET8.  ORACLE9.  MS SqlServer10. MySql11. COM, DCOM

1. How do you register a component?  Compiling the component, running REGSVR32 MyDLL.dll

 2. What does Option Explicit refer to?  All variables must be declared before use. Their type is not required.

 3. What are the different ways to Declare and Instantiate an object in Visual Basic 6?  Dim obj as OBJ.CLASS 

Set obj = New OBJ.CLASS orSet obj = CreateObject (“OBJ.CLASS”) 

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

5. 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. 

6. What are the ADO objects? Explain them. Provide a scenario using three of them to return data from a database.

  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 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.  

7. List out controls which does not have events  shape, line controls

 8. To set the command button for ESC, which Property has to be changed ?  Cancel

 9. What is OLE Used for ?

Object linking and embedding, for using to other object classes like word, excel , autocad objects in our own applications, only thing we have to add reference for these objects 

10 Which controls have refresh method?Checkbox, comna, combo, list, picture, ADo control, Data,Datagrid, Datareport,Dir list biox, filelistbox etc  

11. Early Binding vs Late Binding - define them and explain?Early binding allows developers to interact with the object’s properties and methods during coding permits the compiler to check your code. Errors are caught at compile time. Early binding also results in faster codeEg : Dim ex as new Excel.Application

Late binding on the other hand permits defining generic objects which may be bound to different objectsyou could declare myControl as Control without knowing which control you will encounter. You could then query the Controls collection and determine which control you are working on using the TypeOf method and branch to the section of your code that provides for that typeEg : Dim ex as Objectset ex =CreateObject(“Excel.Application”) 

12. Can I send keystrokes to a DOS application?AppActivate (”C:\windows\system32\cmd.exe”) ‘ Appilcation captionSendKeys (”SA”) ’For sending one stringSendKeys “% ep”, 1 ’ For sending Clipboard data to Dos  

13. How do I make a menu popup from a CommandButtonPrivate Sub Command1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)   If Button = 2 Then       PopupMenu Menuname   End IfEnd Sub 

14. What is Option Base used for in VB6 ?Option Base is to set the Index of the Array to start from 0 or 1.Like option explicit.. declare “Option base 1″ at the top. now the array will start from Index By default the index starts from 0. 

15. How to copy text to the Windows clipboard and from it.Clipboard.SetData and Clipboard.GetData 

16. which method of recordset is used to store records in an array.getrows 

17. What is the default property of datacontrol.Caption 

18 Which property of textbox cannot be changed at runtimeAns : Alignment property, Tab Index etc 

19. Describe In Process and Out of Process component?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 componentAn 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 

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

21. What is the differences between flexgrid  and dbgrid control?Microsoft FlexGrid (MSFlexGrid) control displays and operates on tabular data. It allows programmatically sort, merge, and format tables containing strings and pictures. DBgrid is A spreadsheet-like bound control that displays a series of rows and columns representing records and fields from a ADO Recordset object. 

22. What are different types of ActiveX components available in VB 6.0 ?Standard EXE, ActiveX EXE, ActiveX DLL, ActiveX document, and ActiveX Control 

23. How may type of controls are available in VB6 ?Intrinsic controls - Default controls of VB6, These control are always available in VB6 Toolbox.ActiveX controls - .These are extra controls which can be added into toolbox and this control having separate files (.ocx). Must be deployed separately along with application in other system. 

24. Describe inprocess and out of process ?An in-process component is implemented as a DLL called ActiveX 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 called ActiveX 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. 

25. What is the difference 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. Also picture box is a container control and support most of the graphics method. 

26. What is the difference between a function and a sub (method) ?Function always return a value, wheras am method may or may not return value. 

27. What is the Default property of datacontrol ?Connect property 

28. What are different types of recordset available in ADO ?a) Table-type Recordset - Hold records from single table and can add, edit and delete.b) Dynaset-type Recordset - Can hold editable records from multiple tables.c) Snapshot-type Recordset - Hold read only records from multiple tables,d) Forward-only-type Recordset - Hold read only records from multiple tables without cursor.e) Dynamic-type Recordset -Holds editable records from multiple tables and changes done by other user also visible.

 29. What is the difference between listbox and combo box?

Both are display list of items, however in combo box user can edit the item. 

30. What is the difference modal and moduless window?A modal form has exclusive focus in that application until it is dismissed. Moduless form are not required exclusive focus and it is default when we show any form. 

31. What is the Object and Class?Class is template from we can create objects, Objects are instantiate of a class. For example car is a class and Maruti 800, Maruti Zen are objects of car class. 

32. How objects on different threads communicate with one another?Processes communicate with one another through messages, using Microsoft’s Remote Procedure Call (RPC) technology to pass information to one another. 

33. What is the Query Unload and Unload event in formQuery unload event occurs in a first and then unload event occurs, in MDI form we can trac child form closing status by using this event. 

34. What are different locking type available in ADO.a) LockPessimistic - Locks the row once after any edits occur. b) LockOptimistic - Locks the row only when Update is called. c) LockBatchOptimistic - Allows Batch Updates. d) LockReadOnly - Read only. Cannot alter the data. 

35. Name different ADO Objects?a) Connectionb) Commandc) Recordsetd) Field 

36. What is the difference between a Property Let and Property Set  ?Let used to set value for ordinary variable and Set used to set value for object variable. 

37. What is the difference in passing values ByRef or ByVal to a procedure?a) ByRef -pass the address of variable not valueb) ByVal - pass the value  

38. What is AutoRedraw event of Form and PictureBox ?Automatically redraw the outputs. 

39. What is DoEvents?DoEvents command tell program control to execute other commands, while executing long task. 

40. What is the size of the variant data type?16 bytes 

41. What is the the max length of Text Box?32000 

42. What is the file extensions used in Visual Basic?.frm - Form File, .bas - Module File, .cls - Class File, .res - Resource File,  .ocx - Activex Control, .frx - Form Binary File, .vbp - Visual; Basic Project File, .exe - Executable File. 

43. What is Option Explicit ?It enforce variable declaration. 

44. What are different level of validation available in VB 6.0 ?Field level and form level. 

45. Can we add controls run time?By using control array 

46. How to declare Dll Procedure?Declare function “<Function Name>” lib “<Lib Name>” Alias “<Alias Name>” (Arg, …..) as Return type. 

47. What is Zorder Method of controls?Set the control position in control stack, back and top.  

48. What is Tabstrip control?It is container control, by using tab control we can place more controls. 

49. What is tree view control?Display hierarchy of data like windows explorer. 

50. What is OLE Automation?Call external applications property and method in VB Application. 

51. What is Create Object and Get object?Create object - Create new instance of a class.Get Object - Set reference of exiting object. 

52. What is Static Variable?Static variable retain its value outside of its scope. 

53. What are the scope of the class?Public , private, Friend 

54. How to change the Mouse Pointer in run time?By setting Screen.MousePointer value. 

55. What are the available technologies for accessing database from Visual Basic 6.0?DAO, Data Control, RDO, ODBCDIRECT, ADO, ODBC API. 

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 throughout 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.

What is Friend Variable? Scope sharable between projects.

What is DBFailError? Rolls Back updates if any errors Occurs.

What are the record set types? RdOpenFowardOnly 0 (Default used only for the read only purpose)RdOpenStatic 1RdOpenDynamic 2RdOpenKeySet 3 (Normally used for the live project)

What is the diff between RDO and ADO? RDO is Hierarchy model where as ADO is Object model. ADO can access data from both flat files as well as the data bases. I.e., It is encapsulation of DAO, RDO , OLE that is why we call it as OLE-DB Technology.

Diff types of Lock Types? RdConcurReadOnly 0 (Default)RdConcurLock 1 (Pessimistic Locking)RdConcurRowver 2 (Optimistic Lociking)RdConcurValues 3RdConcurBatch 4

What are the scopes of the class?Public, private, Friend

Have you create Properties and Methods for your own Controls? Properties Public variable of a ClassMethod Public procedure of a class

Private Dim x as integer. Valid ? Private cannot be used in front of DIM.

Different type of Instantiation? Private Only for the Specific Module.Public not creatable Private & PublicMulti Use - Variable we have to declare.Single Use Not possible through dll.Global Multiuse Have variable not Required to Declare.Global Single Use - Only for exe.

What are the different types of Dialog Box? Predefined, Custom, User Defined. 

What is Seek Method which type of record set is available this? Only in DbOpenTables.Syntax: rs.index = "empno"rs.seek "=" , 10If with our setting the rs.index then run time error will occur.

What is Zorder Method? Object.Zorder = 1 or 0 Place a Specified mdiform form or control at the front or back of the z-order with n its Graphical Level.

Can us able to set Instancing properties like Singleuse, GlobalSingleuse to ActiveXDll? No.

What are properties available in Clip Board? No Properties Available. Only the methods they are SetText, GetText, Setdata(), Getformat(), Clear.

What is the different between Microsoft ODBC Driver and Oracle OBDC Driver? Microsoft ODBC driver will support all the methods and properties of Visual Basic. Where as the Oracle not.

What the RDO Methods and Events? Methods EventsBegin Trans ValidateCommit Trans RepositionRollback Trans ErrorCancel Query CompliedRefreshUpdate ControlsUpdate row

What is MAPI ? Messaging Application programming Interface.

What is MDI form? MDI Styles

What are the locks available in Visual Basic?Locking is the process by which a DBMS restricts access to a row in a multi-user environment 4 types of locks. They are1. Batch Optimistic2. Optimistic 3. Pessimistic4. ReadOnly Operations in a relational database act on a complete set of rows. The set of rows returned by a SELECT statement consists of all the rows that satisfy the conditions in the WHERE clause of the statement. This complete set of rows returned by the statement is known as the result set. Applications, especially those that are interactive and online, cannot always work effectively with the entire result set as a unit.

These applications need a mechanism to work with one row or a small block of rows at a time. Cursors are an extension to result sets that provide that mechanism. Cursor or lock type Advantages Disadvantages AdOpenForwardOnly (Default) Low resource requirements Cannot scroll backward No data concurrency AdOpenStatic Scrollable (Wont detect changes made at the same time by another application) No data concurrency AdOpenKeyset Some data concurrency Scrollable Higher resource requirements Not available in disconnected scenario AdOpenDynamic High data concurrency Scrollable Highest resource requirements Not available in disconnected scenario AdLockReadOnly Low resource requirements Highly scalable Data not updatable through cursor AdLockBatchOptimistic Batch updates Allows disconnected scenarios Other users able to access data Data can be changed by multiple users at once AdLockPessimistic Data cannot be changed by other users while locked Prevents other users from accessing data while locked AdLockOptimistic Other users able to access data Data can be changed by multiple users at once

Diff type of Datatypes? LOB (Large Object Data type).CLOB (Stores Character Objects).BLOB ( Store Binary Objects such as Graphic, Video Chips and Sound files).BFILE(Store file pointers to LOB It may Contain filename for photo’s store on CD_ROM).

What is Tabstrip control? Libraries of procedure external to the application but can be called from the application.

What is Static Variable? Its Scope will be available through out the life time.

What is DBSqlPassThrough? It will By Passing the Jet Query Processor.

What is the starting Index value? How to locate it? It is tab control to place our controls with in the form in multiple sheets.Index starts with 1. And to identify If Tabstrip1.SelectedItem.Index = 1 Then ..End if 

What is Parser Bug? It is difficult to use database objects declared in a module from within a form.

What is keyword used to compare to objects? ISOperator Returns Boolean.

Suppose from form1 to form2 object property settings will arise to ? Invalid procedure call or argument (Run time error 5)

What is the return type of Instr and Strcmp? Instr integer (Numeric position)Strcmp - integer ( if both the string are equal they result = 0)Strcmp (Str1, Str2, Comparetype)Comparing mode = 0 Binary Comparing1 Textual Comparing

What is Implicit? Instance of specific copy of a class with its own settings for the properties defined in that class.Note: The implicitly defined variable is never equal to nothing.

What is Inprocess and Out of Process?Inprocess It will run with in the memory. ( Local Machine). Out of Process It will run out of the memory Normally in the server side.

Where will we give the option explicit keyword and for what? In the general declarations section. To trap undeclared variables.

How can we call Stored procedure of Back End in RDO and ADO ? In RDO We can call using RDO Query Objects.In ADO We can call using Command Objects.

What is Static Cursor? In ADO Snap Shot is called so.

How to check the condition in Msgbox? If(Msgbox("Do you want to delete this Record",VbYesNo)=VbYes)Then End if

What is control array and how many we can have it with in the form? Group of control share the same name. Max 32, 767.

What is diff between the Generic Variable and Specific Variable? Generic Variable:Create Object Ex:-Ole-Automation . No need refer the object library.Specific Variable:Binding Procedure Early and Late Binding ( Can be Remove from the Memory).

What is the diff. Between function and sub procedures? Function will return value but a sub procedure wont return values

What is the max size allowed for Extension in Visual Basic? Frm, bas, cls, res, vbx, ocx, frx, vbp, exe 

What is FireHouse Cursors? Forward Only Some time Updateable

With in the form we want to check all the text box control are typed or not? How? For each currentcontrol in controlsif typeof currentcontrol is TextBox thenend ifnext

What are the type of validation available in VB? Field, Form

How to trap Data Base Error? Dim x as RDOErrorX(0).DesX(1).Number

Setting the Cursors.Default Cursor 0ODBC Cursor (Client side) 1ServerSide Cursors (More Network traffic) - 2

How to declare Dll Procedure? Declare function "" lib ""Alias "" (Arg, ..) as Return type.

Referential Integrity (Take care By jet database Engine). Cascade Delete, Cascade Update is done setting property of Attributes.?DbRelationDeleteCascade, DbRelationUpdateCascade.

How to increase the Date corresponding with month,date,year? DateSerial(year(Now),Month(Now)+1,1)Hour, min, sec, month, year, DateSerial, dateadd, datediff, weekday, datevalue, timeserial,timevalue.

Name some date function? Dateadd(), Datediff(), Datepart(), Cdate()

What is difference between datagrid and flexgrid? Datagrid Editable. Flexigrid Non-Editable. (Generally used for Read only purpose.) 

What are two validate with Data Control? Data_Validate, Data_Error.

To connect the Data Control with Back end What are all the properties to be set? Data source Name, Record Source Name

What are the Technologies for Accessing Database from Visual Basic?set? DAO, Data Control, RDO, ODBCDIRECT, ADO, ODBC API , 0040. 

What is the diff between the Create Object and Get object? Create Object - To create an instance of an object.Get Object To get the reference to an existing object.

What is Mask Edit and why it is used? Control. Restricted data input as well as formatted data output.

What is RdExecDirect? Bypasses the Creation of a stored procedure to execute the query. Does not apply to Oracle.

Different type of Passing Value? By value, By ref, Optional, Param Array. Note:- Optional keyword cannot be used while declaring arguments for a function using param array.

What are types of binding? Assigning variable with defined memory space.Late Binding - Memory size is allotted in later stage.Ex:- Dim x as objectEarly Binding - Memory size is allotted while declaring itself. New Key word is important.Ex:- Dim x as New Object

What is Dataware Control?Any control bound to Data Control.Ex:- Textbox, Check Box, Picture Box, Image Control, Label, List box, Combo Box, DB Combo,

What methods are used for DBGrid in unbound mode? AddData, EditData, Readdata, WriteData.

What is ADO? What are its objects ? ActiveX Data Object. ADO can access data from both flat files as well as the databases. I.e., It is encapsulation of DAO, RDO, and OLE that is why we call it as OLE-DB Technology. Objects are Connection, Record Set, Command, Parameter, field, Error, Property.

What is the max size allowed for Max Text box length. 32,000

Record set types and Number available in VB? 3.1- Dynaset, 0 Table, 2 Snap Shot.

What is the max size allowed for Max Control Names length? 255.

How many procedures are in VB? 2.function and sub procedures

What is the max size allowed for Max label caption length.? 2,048 

what will be the result for 15/4 and 154 ? 15/4 = 3.75 and 154 = 3 

What is the max size allowed for Msgbox Prompt and Input Box? 1024

Calling Stored Procedures in VB? 1. Calling Simply the Procedure with out Arguments "Call ProcedureName}"

2. If it is with Arguments Means thenDeclare the Query Def qySet Qy as New Query defQy.SQL = "{Call ProcedureName(?

DSN Less Connection? "Server=Oracle; Driver={Microsoft ODBC for Oracle};"