Visual Basic
Interview Questions and Answers
How
do you register a component?
Compiling the component, running REGSVR32 MyDLL.dll
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
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.
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.
SetComplete and SetAbort.
What
is the tool used to configure the port range and protocols for DCOM
communications?
DCOMCONFIG.EXE
DCOMCONFIG.EXE
What
does Option Explicit refer to?
All variables must be declared before use. Their type is not required.
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.
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.
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.
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
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.
The Parameters collection.
What are some benefits of using MTS?
Database Pooling, Transactional operations, Deployment, Security, Remote Execution.
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.
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.
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.
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.
Yes.
Dim x, y as
integer. What is x and y data type?
X as variant and y as integer.
X as variant and y as integer.
What is
Centralization Error Handling?
Writing function and calling it when error occurs.
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.
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
Vbrun300.dll
Why we use
Treeview Control?
To list the hierarchical list of the node objects. Such of files and Directories.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
Screen.MousePointer = VBHourGlass/VBNormal.
What is Friend
Variable?
Scope sharable between projects.
Scope sharable between projects.
What is
DBFailError?
Rolls Back updates if any errors Occurs.
Rolls Back updates if any errors Occurs.
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)
RdOpenFowardOnly 0 (Default used only for the read only purpose)
RdOpenStatic 1
RdOpenDynamic 2
RdOpenKeySet 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.
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 3
RdConcurBatch 4
RdConcurReadOnly 0 (Default)
RdConcurLock 1 (Pessimistic Locking)
RdConcurRowver 2 (Optimistic Lociking)
RdConcurValues 3
RdConcurBatch 4
What are the scopes of the class?
Public, private, Friend
Public, private, Friend
Have you create
Properties and Methods for your own Controls?
Properties Public variable of a Class
Method Public procedure of a class
Properties Public variable of a Class
Method Public procedure of a class
Private Dim x as integer. Valid ?
Private cannot be used in front of DIM.
Private cannot be used in front of DIM.
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.
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.
What are the
different types of Dialog Box?
Predefined, Custom, User Defined.
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 "=" , 10
If with our setting the rs.index then run time error will occur.
Only in DbOpenTables.
Syntax: rs.index = "empno"
rs.seek "=" , 10
If 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.
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.
No.
What are
properties available in Clip Board?
No Properties Available. Only the methods they are SetText, GetText, Setdata(), Getformat(), Clear.
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.
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 Events
Begin Trans Validate
Commit Trans Reposition
Rollback Trans Error
Cancel Query Complied
Refresh
Update Controls
Update row
Methods Events
Begin Trans Validate
Commit Trans Reposition
Rollback Trans Error
Cancel Query Complied
Refresh
Update Controls
Update row
What is MAPI ?
Messaging Application programming Interface.
Messaging Application programming Interface.
What is MDI
form?
MDI Styles
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 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
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
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).
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.
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.
Its Scope will be available through out the life time.
What is DBSqlPassThrough?
It will By Passing the Jet Query Processor.
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
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.
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.
ISOperator Returns Boolean.
Suppose from
form1 to form2 object property settings will arise to ?
Invalid procedure call or argument (Run time error 5)
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 Comparing
1 Textual Comparing
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
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.
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.
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.
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.
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.
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
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.
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).
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
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
Frm, bas, cls, res, vbx, ocx, frx, vbp, exe
What is
FireHouse Cursors?
Forward Only Some time Updateable
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 controls
if typeof currentcontrol is TextBox then
end if
next
For each currentcontrol in controls
if typeof currentcontrol is TextBox then
end if
next
What are the
type of validation available in VB?
Field, Form
Field, Form
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
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
How to declare
Dll Procedure?
Declare function "" lib ""
Alias "" (Arg, ..) as Return type.
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.
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.
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()
Dateadd(), Datediff(), Datepart(), Cdate()
What is
difference between datagrid and flexgrid?
Datagrid Editable. Flexigrid Non-Editable. (Generally used for Read only purpose.)
Datagrid Editable. Flexigrid Non-Editable. (Generally used for Read only purpose.)
What are two validate with Data Control?
Data_Validate, Data_Error.
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
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.
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.
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.
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.
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.
By value, By ref, Optional, Param Array. Note:- Optional keyword cannot be used while declaring arguments for a function using param array.
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