Top VB questions
1. How do you register a component?
Compiling the component, running REGSVR32 MyDLL.dll
2. Name and explain the different compatibility types
when creating
a COM component
For more stuff & latest JObs visit
www.sureshkumar.net 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
3. Why iss 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.
4. What two methods are called from the ObjectContext
object to
inform MTS that the transaction was successful or
unsuccessful?
SetComplete and SetAbort.
5. What is the tool used to configure the port range
and protocols
for DCOM communications?
DCOMCONFIG.EXE
6. What does Option Explicit refer to?
All variables must be declared before use. Their type
is not
required.
7. 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
8. 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.
9. 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.
10. 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.
11. 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
12. Under the ADO Command Object, what collection is
responsible for
input to stored procedures?
The Parameters collection.
13. What are some benefits of using MTS?
Database Pooling, Transactional operations,
Deployment, Security,
Remote Execution.
14. 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.
15. 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.
16. 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.
17. Can We create CGI scripts in VB??
Yes.
18. Dim x, y as integer. What is x and y data type?
X as variant and y as integer.
19. What is Centralization Error Handling?
Writing function and calling it when error occurs.
20. What is frx?
When some controls like grid and third party control
placed in our
application then it will create frx in run time.
21. What is the Dll required for running the VB?
Vbrun300.dll
22. Why we use Treeview Control?
To list the hierarchical list of the node objects.
Such of files and
Directories.
23. Handling Error in Calling chain.
This will call the top most error where the error is
handled.
24. In project properties if we set Unattended what is
it mean?
This cannot have user interface. This can be used for
the COM
creation.
25. 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.
26. What is view Port?
The area under which the container provides the view
of the ActiveX
Document is known as a view port.
27. What are the different types of error?
Syntax Errors, Runtime , Logic.
28. 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.
29. What is Mixed Cursors?
Static + Keyset
30. 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.
31. What are the Style Properties of Combo Box?
Simple, Dropdown list We can type and select. Dropdown
Combo Only
Drop Down.
32. What are the Style properties of List Box?
Simple Single Select , Extended. Multiple Select.
33. 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.
34. 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.
35. How to change the Mouse Pointer?
Screen.MousePointer = VBHourGlass/VBNormal.
36. What is Friend Variable?
Scope sharable between projects.
37. What is DBFailError?
Rolls Back updates if any errors Occurs.
38. What are the record set types?
RdOpenFowardOnly 0 (Default used only for the read
only purpose)
RdOpenStatic 1
RdOpenDynamic 2
RdOpenKeySet 3 (Normally used for the live project)
39. 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.
40. Diff types of Lock Types?
RdConcurReadOnly 0 (Default)
RdConcurLock 1 (Pessimistic Locking)
RdConcurRowver 2 (Optimistic Lociking)
RdConcurValues 3
RdConcurBatch 4
41. What are the scopes of the class?
Public, private, Friend
42. Have you create Properties and Methods for your
own Controls?
Properties Public variable of a Class
Method Public procedure of a class
43. Private Dim x as integer. Valid ?
Private cannot be used in front of DIM.
44. Different type of Instantiation?
Private Only for the Specific Module.
Public not creatable Private & Public
Multi 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.
45. What are the different types of Dialog Box?
Predefined, Custom, User Defined.
46. What is Seek Method which type of record set is
available this?
Only in DbOpenTables.
Syntax: rs.index = "empno"
rs.seek "=" , 10
If with our setting the rs.index then run time error
will occur.
47. 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.
48. Can us able to set Instancing properties like
Singleuse,
GlobalSingleuse to ActiveXDll?
No.
49. What are properties available in Clip Board?
No Properties Available. Only the methods they are
SetText, GetText,
Setdata(), Getformat(), Clear.
50. 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.
51. What the RDO Methods and Events?
Methods Events
Begin Trans Validate
Commit Trans Reposition
Rollback Trans Error
Cancel Query Complied
Refresh
Update Controls
Update row
52. What is MAPI ?
Messaging Application programming Interface.
53. What is MDI form?
MDI Styles?
54. 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 are
1. Batch Optimistic
2. Optimistic
3. Pessimistic
4. 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
55. 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).
56. What is Tabstrip control?
Libraries of procedure external to the application but
can be called
from the application.
57. What is Static Variable?
Its Scope will be available through out the life time.
58. What is DBSqlPassThrough?
It will By Passing the Jet Query Processor.
59. 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
60. What is Parser Bug?
It is difficult to use database objects declared in a
module from
within a form.
61. What is keyword used to compare to objects?
ISOperator Returns Boolean.
62. Suppose from form1 to form2 object property
settings will arise
to ?
Invalid procedure call or argument (Run time error 5)
63. 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 Comparing
1 Textual Comparing
64. 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.
65. 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.
66. Where will we give the option explicit keyword and
for what?
In the general declarations section. To trap
undeclared variables.
67. 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.
68. What is Static Cursor?
In ADO Snap Shot is called so.
69. How to check the condition in Msgbox?
If(Msgbox("Do you want to delete this
Record",VbYesNo)=VbYes)Then
End if
70. 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.
71. 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).
72. What is the diff. Between function and sub
procedures?
Function will return value but a sub procedure wont
return values
73. What is the max size allowed for Extension in
Visual Basic?
Frm, bas, cls, res, vbx, ocx, frx, vbp, exe
74. What is FireHouse Cursors?
Forward Only Some time Updateable
75. With in the form we want to check all the text box
control are
typed or not? How?
For each currentcontrol in controls
if typeof currentcontrol is TextBox then
end if
next
76. What are the type of validation available in VB?
Field, Form
77. How to trap Data Base Error?
Dim x as RDOError
X(0).Des
X(1).Number
Setting the Cursors.
Default Cursor 0
ODBC Cursor (Client side) 1
ServerSide Cursors (More Network traffic) - 2
78. How to declare Dll Procedure?
Declare function "" lib ""
Alias "" (Arg, ..) as Return type.
79. Referential Integrity (Take care By jet database
Engine).
Cascade Delete, Cascade Update is done setting
property of
Attributes.?
DbRelationDeleteCascade, DbRelationUpdateCascade.
80. 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.
81. Name some date function?
Dateadd(), Datediff(), Datepart(), Cdate()
82. What is difference between datagrid and flexgrid?
Datagrid Editable. Flexigrid Non-Editable. (Generally
used for Read
only purpose.)
83. What are two validate with Data Control?
Data_Validate, Data_Error.
84. To connect the Data Control with Back end What are
all the
properties to be set?
Data source Name, Record Source Name
85. What are the Technologies for Accessing Database
from Visual
Basic?set?
DAO, Data Control, RDO, ODBCDIRECT, ADO, ODBC API ,
0040.
86. 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.
87. What is Mask Edit and why it is used?
Control. Restricted data input as well as formatted
data output.
88. What is RdExecDirect?
Bypasses the Creation of a stored procedure to execute
the query.
Does not apply to Oracle.
89. 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.
90. What are types of binding?
Assigning variable with defined memory space.
Late Binding - Memory size is allotted in later stage.
Ex:- Dim x as object
Early Binding - Memory size is allotted while
declaring itself. New
Key word is important.
Ex:- Dim x as New Object
91. 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,
92. What is the default model of the form? And what is
it number?
93. Why we need OLE-Automation? Advantages?
94. What methods are used for DBGrid in unbound mode?
AddData, EditData, Readdata, WriteData.
95. 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.
96. What is the max size allowed for Max Text box
length.
32,000
97. Record set types and Number available in VB?
3.
1- Dynaset, 0 Table, 2 Snap Shot.
98. What is the max size allowed for Max Control Names
length?
255.
99. How many procedures are in VB?
2.
function and sub procedures
100. What is the max size allowed for Max label
caption length.?
2,048
101. what will be the result for 15/4 and 154 ?
15/4 = 3.75 and 154 = 3
102. What is the max size allowed for Msgbox Prompt
and Input Box?
1024
103. Calling Stored Procedures in VB?
1. Calling Simply the Procedure with out Arguments
"Call
ProcedureName}"
2. If it is with Arguments Means then
Declare the Query Def qy
Set Qy as New Query def
Qy.SQL = "{Call ProcedureName(?
104. DSN Less Connection?
"Server=Oracle; Driver={Microsoft ODBC for Oracle};"
105. Visual Basic Interview Questions only
1. 3 main differences between flexgrid control and
dbgrid control
2. ActiveX and Types of ActiveX Components in VB
3. Advantage of ActiveX Dll over Active Exe
4. Advantages of disconnected recordsets
5. Benefit of wrapping database calls into MTS
transactions
6. Benefits of using MTS
7. Can database schema be changed with DAO, RDO or
ADO?
8. Can you create a tabletype of recordset in Jet -
connected ODBC
database engine?
9. Constructors and distructors
10. Controls which do not have events
11. Default property of datacontrol
12. Define the scope of Public, Private, Friend
procedures?
13. Describe Database Connection pooling relative to
MTS
14. Describe: In of Process vs. Out of Process
component. Which is
faster?
15. Difference between a function and a subroutine,
Dynaset and
Snapshot,early and late binding, image and picture
controls,Linked
Object and Embedded Object,listbox and combo
box,Listindex and Tab
index,modal and moduless window, Object and
Class,Query unload and
unload in form, Declaration and Instantiation an
object?
16. Draw and explain Sequence Modal of DAO
17. How can objects on different threads communicate
with one
another?
18. How can you force new objects to be created on new
threads?
19. How does a DCOM component know where to
instantiate itself?
20. How to register a component?
21. How to set a shortcut key for label?
22. Kind of components can be used as DCOM servers
23. Name of the control used to call a windows
application
24. Name the four different cursor and locking types
in ADO and
describe them briefly
25. Need of zorder method, no of controls in form,
Property used to
add a menus at runtime, Property used to count number
of items in a
combobox,resize a label control according to your
caption.
26. Return value of callback function, The need of
tabindex property
27. Thread pool and management of threads within a
thread pool
28. To set the command button for ESC, Which property
needs to be
changed?
29. Type Library and what is it's purpose?
30. Types of system controls, container objects, combo
box
31. Under the ADO Command Object, what collection is
responsible for
input to stored procedures?
32. VB and Object Oriented Programming
33. What are the ADO objects? Explain them.
34. What are the different compatibility types when we
create a COM
component?
35. What do ByVal and ByRef mean and which is the
default?
36. What does Option Explicit refer to?
37. What does the Implements statement do?
38. What is OLE and DDE? Explain.
39. What is the difference between Msgbox Statement
and MsgboxQ
function?
40. What keyword is associated with raising system
level events in
VB?
41. What methods are called from the ObjectContext
object to inform
MTS that the transaction was successful or
unsuccessful?
42. What types of data access have you used.
43. What was introduced to Visual Basic to allow the
use of Callback
Functions?
44. Which controls can not be placed in MDI?
45. Which controls have refresh method, clear method
46. Which Property is used to compress a image in
image control?
47. Which property of menu cannot be set at run time?
48. Which property of textbox cannot be changed at
runtime and
What's the maximum size of a textbox?
49. Which tool is used to configure the port range and
protocols for
DCOM communications?
50. What is Dll?
51. Question How many images can be placed in the
image list?
52. What is the result of Null * Any value = 0 (Zero)?
