Visual Basic Interview Questions 4

81 Advatages of ADO?
i) Flat Object Mode:
ADO either this kind of hierarchical creation can be followed or its object
can be created independently.
2) Less number of objects
ADO does not have large ammount of objects like DAO and RDO, which leadsdifficulty in coding. ADO objects set is less than DAO and RDO but more powerful.
3) Direct assignment to DataBound controls:
To fill DataBound contorls its data source property can be set to a record set object instead of setting to a DataControl.
4) Enhanced Performance by recordset object:
Indexed fileds greatly enhanced the performance of the recordset object using find method sort and filter properties.
5) Recordset Persistence
Recordset data can saved in a file. The "MSPersist Provider" supports storing a recordset object in a file with the record set object save method.


82 How many ways we can access file using VB?
i) Open "" for Binary/Input/Output/Append/Random as #FilePointer
ii) Usig File Systm object
161 How to get freefile location in memory?
Dim fn as long
fn=FreeFile()
162 How to find size of the file. Which method or function is used to occomplish this?
DIM L#
L=FileLen("FilePath")
163 Using which type we can access file line by line?
Dim FN#, X$
FN = FreeFile()
Open "c:\EX.TXT" For Input As #FN
While (EOF(FN) = False)
Input #FN, X
MsgBox X
Wend
Close #FN
164 Which method is used to write context Into file?
PRINT #FINENO,DATA
165 How can you read content from file?
INPUT #FN,
166 Binary Access-method is used to access file in which manner?
167 How can you check Beginning and End of the file?
168 What is the use of Scalewidth and ScaleHeight Proeperty?
Returns/sets the number of units for the horizontal measurement
of an objects interrior.
169 What is the use of Active Control Property?
Object=Me.ActiveControl
This property returns the address of the object which has
the current focus on the form.
170 How can you save and Get data from Clipboard
clipBoard.SetText(Data)
x=ClipBoard.GetText()
171 What are the types of Error?
Syntax Error
Logical Error
Run-Time Error
172 In which areas the Error occurs?
173 What are the tools available for Debugging in VB?
Local Window, Watch Window, Immediate Window,
174 What is the use of Immediate, Local Window and Watch Window?
Immediate Window
While experimenting with an application, it may be
desirable to execute individual procedure, evaluate expressions
or assign new values to variables or properties. This Immediate
window helps to accomplish these tasks.
To print in Immediate Window:
----------------------------
i) By including Debug.Print statement in the application
code.
ii) By entering Print method directly in the immediate
Window.
Local Window:
This window shows the value of any variables with in the
scope of the current procedure. As the execution switch as
from procedure to procedure, the contents of the local window
change to reflect only the variables applicable to current
procedure.
Watch Window:
An expression can be added by draging it from the code
editor and dropping at the watch window.
QuickWatch Window:
Helps to check the value of property, variable or
expression for which the watch expression is not defined.
176 How can you Implement windows functionality in VB?
Application Programming Interface.
177 How many types of API functions are availble in VB?
There are five types
1) Windows Management(User)
2) Graphics Device Interface (GDI)
3) System Services
4) Multimedia
178 How can you Add API functions to your Application?
Select Add_Ins-> Add-In Manager -> Check Loaded/UnLoaded --> Ok
179 How to get Cursor position using API?
Option Explicit
Private Declare Function GetCursorPos Lib "user32" (lpPoint As POINTAPI) As Long
Private Type POINTAPI
x As Long
y As Long
End Type
Dim P As POINTAPI
Private Sub Form_Activate()
While (1)
Call GetCursorPos(P)
DoEvents
Me.Caption = P.x & ", " & P.y
Wend
End Sub
180 Is it possible to change menu runtime using API? If yes? Specify the function names.
216 What do you mean ByVal and ByRef and which is the default?
ByVal -Copy of the value is passed to the function parameter.
-The changes in the procedures will not affect the actual argument.
ByRef -The calling procedure passes the address of the variable in memory so that the procedure can change the value of the actual argument.
* The default is "ByRef"
252 Describe the different scopes of variables in VB.
Local variables:
Declared in any event, subroutine, or function with the keywords Dim or Static. These variables only exist within the context of the procedure in which they are declared. There is no problem with having local variables in many procedures with the same name. They all will refer to different storage spaces. If there is a conflict in names between a local variable and a more global variable, the local variable always wins. Use Static only if you don't want to lose the value in a local variable between calls to the procedure. Usually you will use Dim.
Module-level variables:
Declared in a form or BASIC module's General Declarations section, with the keywords Dim or Private. Dim is the old syntax; Private is preferred. These variables are accessible from any event, subroutine, or function procedure in the module.

old: Global variables:
Declared in any Basic Module in the project using the keyword "Global". These variables can be accessed and changed by any procedure in the project. It's best to avoid these and use the new "Public" type.
new: Public variables:
These are declared in a form or BASIC module's General Declarations section. They belong to the module in which they are declared, but they can be accessed from any procedure in the project.

253 Describe the difference between a public variable in a form and one in a standard code
module.
255 What are some uses and misuses of variants?
A variant data type can hold any type of data. Again, this may seem useful, but it has disadvantages. The largest disadvantage is performance. At run time, VBA must execute good amount of code each time you access the variable to determine what sort of data already exists in the variable, and what sort of data you're setting the variable to. Also, it will execute code to convert from one type to another when you are calling other procedures.
In a large application with lots of variables, this can add up to a great deal of overhead. There are some instances in which you will want to use a variant, such as when using the Split function. If you need a variant data type, explicitly declare it as such. This will make the code easier to interpret and debug in the future.


256 What are some of the steps you can take to determine why your program is crashing with "Invalid Page Fault" errors?
re: invalid page fault in Kernel32.dll
Gevie: among the many possibilities, these appear likely:
1. your browser needs updating. the first link below after your text can be
used for that.
2. your password list is damaged. the second link below has the resolution for
that.
3. your anti-virus program needs updating or a patch.

260 Dim x, y as integer. What is x and y data type?
X as variant and y as integer.
261 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)
262 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 Co...
263 What is the max size allowed for Msgbox Prompt and Input Box?
1024
264 What is the max size allowed for Max label caption length.
2,048
265 What is the max size allowed for Max Text box length.
32,000
266 What is the max size allowed for Max Control Names length
255.
267 What is the max size allowed for Extension in Visual Basic
Frm, bas, cls, res, vbx, ocx, frx, vbp, exe
268 What is frx?
When some controls like grid and third party control placed in our application then it
will create frx in run time.
269 Name some date function
Dateadd(), Datediff(), Datepart(), Cdate()
270 what will be the result for 15/4 and 154 ?
15/4 = 3.75 and 154 = 3
271 What is keyword used to compare to objects?
ISOperator - Returns Boolean.
272 How many procedures are in VB?
a) Function
b) Sub Procedures
273 what is the diff. Between function and sub procedures
Function will return value but a sub procedure wont return values…
274 Where will we give the option explicit keyword and for what?
In the general declarations section. To trap undeclared variables.
275 What is Friend Variable?
Scope sharable between projects.
276 What is binding?
"Binding" means exposing the client object model to the host application
277 What are the types of binding?
Assigning variable with defined memory space.
Late Binding -
Memory size is allotted at run-time. It is bound to any type
specifically.
Ex:- Dim x as object
Early Binding -
The compiler knows the type of the variable and will not compile
lines that reference nonexistent properties or methods
Eg: Dim X as TextBox
set X=Text1
Advantages:
a) Code is shorter
b) Code execute faster
c) There are fewer run-time errors
278 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.
279 What is Mask Edit and why it is used?
Control. Restricted data input as well as formatted data output.
280 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.
281 What are the type of validation available in VB?
Field, Form
282 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
283 What is the result of Null * Any value = 0 (Zero)?
284 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.
285 What is the default model of the form?
286 Suppose from form1 to form2 object property settings will arise to ?
Invalid procedure call or argument (Run time error - 5)
288 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...


289 How to declare Dll Procedure?
Declare function "" lib "" Alias "" (Arg, …..) as
Return type.
290 What is MDI form? MDI Styles?
291 How many images can be placed in the image list?
64
293 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 Conta...
294 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.
295 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).
296 What are properties available in Clip Board?
No Properties Available.
Only the methods they are SetText, GetText, Setdata(), Getformat(), Clear.
297 What is Dll?
Libraries of procedure external to the application but can be called from the application.
298 What is Tabstrip control?
299 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
302 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.
303 Have you create Properties and Methods for your own Controls?
Properties - Public variable of a Class
Method - Public procedure of a class
304 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 membe...
305 What is Static Variable?
Its Scope will be available through out the life time.
306 Private Dim x as integer. Valid ?
Private cannot be used in front of DIM.
307 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.
308 What are the scopes of the class?
Public, private, Friend
309 Can us able to set Instancing properties like Singleuse, GlobalSingleuse to ActiveXDll?
--------------No---------------
311 What are the Style Properties of Combo Box?
DropdownList,Simple - We can type and select.
Dropdown Combo - Only Drop Down.
312 What are the Style properties of List Box?
Simple -Single Select
Extended. - Multiple Select.
356 Implement smooth scrolling for either text, graphics or controls across a form.
357 Implement some quick and easy encryption (can be something primitive).
358 Four different types of sorts: advantages and disadvantages.

Predefined, Custom, User Defined.
314 What is Parser Bug?
It is difficult to use database objects declared in a module from within a form.
315 What is the Dll required for running the VB?
Vbrun300.dll
316 Can We create CGI scripts in VB?
Yes.
317 How to change the Mouse Pointer?
Screen.MousePointer = VBHourGlass/VBNormal.
318 How to check the condition in Msgbox?
If(Msgbox("Do you want to delete this Record",VbYesNo)=VbYes)Then End if
319 What is difference between datagrid and flexgrid?
Datagrid - Editable.
Flexigrid - Non-Editable. (Generally used for Read only purpose.)
321 What is Dataware Control?
Any control bound to Data Control.
Ex:- Textbox, Check Box, Picture Box, Image Control, Label, List box, Combo Box,
DBCombo,
322 What are two validate with Data Control?
Data_Validate, Data_Error.
323 Record set types and Number available in VB?
3. 1- Dynaset, 0 - Table, 2 - Snap Shot.
324 Referential Integrity (Take care By jet database Engine).
Cascade Delete, Cascade Update - is done setting property of Attributes.
DbRelationDeleteCascade, DbRelationUpdateCascade.
326 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 Te...
327 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.
328 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.
329 What are the Technologies for Accessing Database from Visual Basic?
DAO, Data Control, RDO, ODBCDIRECT, ADO, ODBC API , 0040.
331 What is MAPI ?
Messaging Application programming Interface.
332 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.
333 What are the different types of error?
Syntax Errors, Runtime , Logic.
334 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.
335 What is Centralization Error Handling?
Writing function and calling it when error occurs.
336 Handling Error in Calling chain.
This will call the top most error where the error is handled.
337 To connect the Data Control with Back end What are all the properties
to be set?
Data source Name, Record Source Name
338 How to trap Data Base Error?
Dim x as RDOError
X(0).Desc
X(1).Number
339 What is view Port?
The area under which the container provides the view of the
ActiveX Document is known as a view port.
340 What methods are used for DBGrid in unbound mode?
AddData, EditData, Readdata, WriteData.
341 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.
342 Setting the Cursors.
Default Cursor - 0
ODBC Cursor (Client side) - 1
ServerSide Cursors (More Network traffic) - 2
345 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
346 What is Static Cursor?
In ADO Snap Shot is called so.
356 Implement smooth scrolling for either text, graphics or controls across a form.
357 Implement some quick and easy encryption (can be something primitive).
358 Four different types of sorts: advantages and disadvantages.

Static + Keyset
348 What is FireHouse Cursors?
Forward Only Some time Updateable
349 What is DBSqlPassThrough?
It will By Passing the Jet Query Processor.
350 What is DBFailError?
Rolls Back updates if any errors Occurs.
351 DSN Less Connection?
"Provider=MSDASQL;Driver={Microsoft ODBC for Oracle};Server=Oracle"
352 What is RdExecDirect?
Bypasses the Creation of a stored procedure to execute the query.
Does not apply to Oracle.
353 How do you center a form?
In the form properties, the startup position property is having two
option regarding Center the form.
1. 1-Center Owner :- The form will be made centered based on the
current form that calls the form.
i.e., if already one form is opened then the next form will be
the center to that form which will be called.
2. 2-Center Screen :- I hope no need of any explanation for this.

354 Can I send keystrokes to a DOS application?
Windows keybd_event command which will send keystrokes to a DOS application.

355 Convert an RGB value to a long, or a long to RGB.

Converting an RGB Value to Long
LongVar = BlueValue * 65536 + GreenValue * 256 + redValue
'Converting a Long to RGB
RedValue = LongValue Mod 256
GreenValue = ((LongValue And &HFF00) / 256&) Mod 256&
BlueValue = (LongValue And &HFF0000) / 65536
359 Compute CRC32 checksum, write a quick piece of code that accepts the packet of data and
returns the CRC.
360 How do you use the Mouse OFF event?
361 How do I call Windows Help files from a VB program?
Option Explicit
Private Declare Function WinHelp Lib "user32? Alias "WinHelpA" _
(ByVal hwnd As Long, ByVal lpHelpFile As String, _
ByVal wCommand As Long, ByVal dwData As Long) As Long
Private Const HELP_CONTENTS = 3
Private Const HELP_FINDER = 11
Private Sub Command1_Click()
Dim lResult As Long
Dim sHelpFile As String
Dim lCommand as Long, lOption as Long
sHelpFile = "winfile.hlp"
lCommand = HELP_CONTENTS
lOption = 0
lResult = WinHelp(Me.hwnd, sHelpFile, lCommand, lOption)
End Sub
368 How to copy text to the Windows clipboard and from it.
dim X$, Y$
x=ClipBoard.GetText()
ClipBoard.Clear()
ClipBoard.SetText("THIS IS MINE")
369 How can I call a Command button without clicking it?
Command1.Value=1
370 Write a simple app with Encrypt and Decrypt buttons
and Textbox where the user can enter text for
encryption and decryption.
371 Three main differences between flexgrid control and dbgrid control



373 Advantage of ActiveX Dll over ActiveX Exe .
Advantages of Dll over Exe:-
Dll is faster WRT exe, because dll runs within
the same process space of its client
where as exe runs on its own process space.
Difference :-
1. Dll is faster than exe
2. dll is in-process whereas exe is out-process

378 Controls which do not have events
Line, Shape, Label
379 Default property of datacontrol
NAME
380 Define the scope of Public, Private, Friend procedures?
384 image and picture controls, linked object and embedded Object,
listbox and combo box,Listindex and Tab index,modal and moduless window,
394 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. Return value of callback function, The need of tabindex property
397 Types of system controls, container objects, combo box
Under the ADO Command Object, what collection is responsible
for input to stored procedures?
414 What is the maximum size of a textbox?
32,000
415 Which tool is used to configure the port range and protocols
for DCOM communications?
416) Explain about ACID property?
Atomicity:
All or none, either every part of a transaction gets completed,
or none of it does at all. If everything works correctly without
any errors, everything gets committed to the database. If any one
part of the transaction fails, the entire transaction gets rolled back.
Consistency:
This property ensures that the state of the database is the same
when it ends as it was when it began, and that no rules or constraints
of the database are violated as a result of the transaction.
Any violation of rules or constraints will cause the transaction to fail.
Isolation:
The operations that take place within a transaction are isolated from
the operations of other transactions or other database operations, and
that no other transaction or operation can have access in any way to the data that's being affected by a transaction in it's intermediate state
(while the transaction is taking place).
Durability:
The guarantee that once a transaction has completed, the results of it
will persist and remain accurate and stable within the database.
417) How to open multirecordset in a Recordset Objects.
dim Conn as Connection
dim Rs as Recordset, SQL$
set Conn=CreateObject("ADODB.Connection")
set rs =CreateObject("ADODB.Recordset")
sQL="SELECT * FROM EMP; SELECT * FROM DEPT"
rs.open SQL, CONN, adForwardOnly, adLockReadOnly
while(rs.EOF=False) 'Reading Emp Data
:
:
rs.MoveNext
Wend
rs.NextRecordSet
while(rs.EOF=False) 'Reading Dept Data
:
:
rs.MoveNext
Wend
:
:





421) Diffence between Global Variable & Public Variable?
old: Global variables:
Declared in any Basic Module in the project using the keyword "Global". These variables can be accessed and changed by any procedure in the project. It's best to avoid these and use the new "Public" type.
new: Public variables:
These are declared in a form or BASIC module's General Declarations section. They belong to the module in which they are declared, but they can be accessed from any procedure in the project.
422) When a form is executed what are the sequence of events executes?
a) Form_Initialize
b) Form_Load
c) Form_Activate
d) Form_GotFocus

423) How to retrive and Store Image into DataBase?

Private Sub LoadFromTable()
Dim FilePath$, Fp%, Size&, Count&, Data() As Byte
FilePath = App.Path & "\Temp.BMP"
If (Dir(FilePath) <> "") Then Kill (FilePath)
Size = rs("Photo").ActualSize
Fp = FreeFile
Open FilePath For Binary As #Fp
While (Count < Size)
Data() = rs("Photo").GetChunk(100)
Put #Fp, , Data
Count = Count + 100
Wend
Close #Fp
Picture1.Picture = LoadPicture(FilePath)
Kill (FilePath)
End Sub
Private Sub SaveToTable()
Dim bytBLOB() As Byte
Dim strImagePath As String
Dim intNum As Integer
'Save the record
strImagePath = Picture1.Tag
rs.AddNew
'Open the picture file
intNum = FreeFile
Open strImagePath For Binary As #intNum
ReDim bytBLOB(FileLen(strImagePath))
'Read data and close file
Get #intNum, , bytBLOB
Close #1
'Store the BLOB
rs.Fields("PHOTO").AppendChunk bytBLOB
rs.Update
End Sub


424) How to access INI file from VB?
// Functions
Function GetFromINI(sSection As String, sKey As String, sDefault As String, sIniFile As String)
Dim sBuffer As String, lRet As Long
'Fill String with 255 spaces
sBuffer = String$(255, 0)
'Call DLL
lRet = GetPrivateProfileString(sSection, sKey, "", sBuffer, Len(sBuffer), sIniFile)
If lRet = 0 Then
'DLL failed, save default
GetFromINI = sDefault
Else
'DLL successful,Return string
GetFromINI = Left(sBuffer, InStr(sBuffer, Chr(0)) - 1)
End If
End Function

'// Returns True if successful. If section does not
'// exist it creates it.
Function AddToINI(sSection As String, sKey As String, sValue As String, sIniFile As String) As Boolean
Dim lRet As Long
'Call DLL
lRet = WritePrivateProfileString(sSection, sKey, sValue, sIniFile)
AddToINI = lRet
End Function
==============================================================================
Code: Calling a Parameterized Stored Procedure (Visual Basic)
This example shows how to pass a parameter and execute a stored procedure.
Example
Dim SprocCommand As New SqlClient.SqlCommand
SprocCommand.Connection = dcNorthwind
SprocCommand.CommandType = CommandType.StoredProcedure
SprocCommand.CommandText = "CustOrderHist"
Dim CustomerIDParam As New SqlClient.SqlParameter("@CustomerID", TextBox1.Text)
SprocCommand.Parameters.Add(CustomerIdParam)
Dim SprocResults As SqlClient.SqlDataReader
Try
dcNorthwind.Open()
SprocResults = SprocCommand.ExecuteReader()
' Process SprocResults datareader here.
Catch ex As Exception
MessageBox.Show("Failed to execute command")
Finally
dcNorthwind.Close()
End Try


420) Define Component Object Model?
a) The COM is specification for a way of creating components and building application from these components.
b) Entirely new application can be build from existing components.
c) A component is like a mini-application that is compiled, linked and ready to use.
d) It connects with other components at run-time to form an appliation
e) Modifying or enhancing the application is a simple matter of replacing one of these
constituent component with a new version.
eg: DA0 3.51 is component used by many appliation when it new version say 4.0 arrives the old component can simply be replaced without the necessity of compiling the application that use them.


Benifits of COM
===============
a) Application customization
Application can easily be customized by adding new components or changing existing components.
b) Component Libraries
Components are implemented in DLLs. So they can be linked with the application at run-time.
c) ActiveX
This is a new technology that is based on OLE & COM. ActiveX replaces the VBXand OLE control architecture. This can be one of the following
i) ActiveX control- (Ocx)
It is a Software component that can be used in variety of application developed by diffent kinds of programming languages such as VB, VC++,Java
ii) Activex Server (ActiveX Exe & ActiveX DLL)- COde components.
These are applications that expose the functionality through interface consisting of properties, methods and events.
iii) ActiveX Document
These are application that can be hosted in containers such as IE and Office Binder.
310 In project properties if we set Unattended what is it mean?
This cannot have user interface. This can be used for the COM creation. If your component is an ActiveX EXE marked for unattended execution (that is, it has no user interaction whatever), and the Instancing property of the Widget class is set to MultiUse, the result of both scenarios above is that two Widget objects are created in same copy of SmallMechanicals, each on its own thread of execution.
215 What are the different compatibility types when we create a COM component?
a) NO CAMPATIBILITY
This compatibility is a poor choice, because by-default VB creates a new new GUID and TypeLib every time compile, quickly filling the Registry with
dangling entries.
b) PROJECT COMPATIBILITY
VB knows to use the existing GUID and type library rather than create new ones. This also allows any existing Registry entries to be reused. resulting in much less clutter in the Registry. This also means projects that use your control need not be completely rebuilt,since the GUID has not changed. Therefore, any application that uses the control will still contain valid pointers to it.
c) BINARY COMPATITBILITY
This compatibility is used when you are ready to ship your control. Choose Binary Compatibility and in the textbox enter the component(ocx, dll, exe) with which you want maintain interface compatibility.This option compare s saved copy of our project(ocx, dll, exe) to verify that no exposed properties, methods or events have changed in new version.If any changes to existing exposed properties, events or methods, VB will notify you with a dialog indicating what has changed. You then have the option of canelling the compile to remove the changes or compiling and creating new version.
422) What is COM+?
COM+ is the name of the COM-based services and technologies first released in Windows 2000. COM+ brought together the technology of COM components and the application host of Microsoft Transaction Server (MTS).
COM+ automatically handles difficult programming tasks such as resource pooling, disconnected applications, event publication and subscription and
distributed transactions
425) DCOM
Short for Distributed Component Object Model, an extension of the Component Object Model(COM) that allows COM components to communicate across network boundaries. Traditional COM components can only perform interprocess communication across process boundaries on the same machine. DCOM uses the RPC mechanism to transparently send and receive information between COM components (i.e., clients and servers) on the same network. DCOM was first made available in 1995 with the initial release of Windows NT 4.
DCOM serves the same purpose as IBM's DSOM protocol, which is the most popular implementation of CORBA. Unlike CORBA, which runs on many operating systems, DCOM is currently implemented only for Windows.