VB.NET Flashcards
Disadvantages of vb ?
Following are the disadvantage of VB :
1. VB is not object oriented.
2. VB DLL does not support side-by-side execution
3. Deployment is time consuming as all the components must
be registered in the Windows registry.
[.The VB support OOP concepts, but not support fully.
2.VB does not support exception handling.
3.No multithreading mechanism.]
Advantage of vb.net over vb ?
1,supports Threading 2,powerful Exception handling mechanism 3,having support for the console based applications 4,More than one version of dll is supported [1. VB is object based while Vb.net is Object oriented 2. VB.net using OO functionality like inheritenc a, Excepetional handling, etc 3.VB .net is strong type casting which VB lack 4.VB.net supports multi threading....]
What is intermediate language in .NET ?
.net supports CLS i. e. Common language type. its a microsoft’s feature to bring all languages near one roof.
When You compile .net code it doesn’t converted into binary language, it converted into IL (Intermediate Language) also known as MSIL.
And from IL to binary language converted at run time, CLR manages this process. At the runtime also it not converts whole project at time to binary, only converts that part which is going to execute, this the performance of project increases. This IL can use any language which is
member of that .net studio. The assemblies (ExE, DLL) are also in IL form. So u can use any EXE or DLL created in vb.net in c#.net also.[which converts native code into byte code i.e machine understandable code.]
Is VB.NET object oriented? What are the inheritances does VB.NET support ?
yes VB.NET ia an object oriented.
Vb.net supports all inheritance
1)single inheritance
It means Single class inheriting to single child classes
2)multiple inheritance
multiple classess inherits to single classes
3)Multilevel Inheritance
Single class inherits to one class that class inheritd to single another class
4)Heirarichal inheritance
Single class inherits to Multiple classes
5)Hybrid Inheritance
Single class inherits to different classess and that classes inherits to one class
Difference between VB dll and assemblies in .NET ?
Assemblies can contain DLL and EXE both. Different versions of one DLL can be handled by assemblies. They overcome the DLL Hell problem.
Assemblies Contain Manifest and Meta Data files. These are the separate files that describes the Assembly and its attributes. VB DLL is inprocess.
DLL run with an exe where as DLL are not self executable.
we can reuse DLLs .DLL are not platform independent If we have more then one Versions of a DLL we can face DLL Hell Problem.
How do you do multithreading application in VB ?
VB doesn’t support multithreading.
[Its the fastest and an excellent application provided in VB.net. Due to which many operations can be done without any lapse of time.
The system need not wait for an application or any task to get completed, rather it runs simultaneously.]
.what are the advantage in vb.net and different between vb and vb.net?
vb is not follow the oops concept. But vb.net follow the oops concept.
[Adv of VB.NET vb is object based.vb.net is object oriented vb use record set for database connection vb.net use dataset for database connection]
[1. VB uses vb runtime while vb.net uses CLR
2. VB object based,vb.net is object oriented
3. VB Suports splash screen
4. VB Uses on error goto while vb.net uses Try..
Catch..Finally
5. vb.Net Supports inheritance]
What is the Difference between Web User Control and Web Custom Control?
web user control where it predefined attribute functionality where it resides in control library web custom control: where it is defined by
user itself and store in a custom library
[Web User Controls:
1) Easy to Create
2) Limited support for consumers who use visual design tool
3) A seperate copy of the control is required in each
application.
4)Cannot be added to toolbox in Visual Studio.
5) Good for Static Layout
Web Custom Controls:
1) Harder to Create
2) Full support for consumers
3) Only a single copy of the control is required in the GAC
4)Can be added
5) Good for Dynamic Layout]
What is an indexed property?
you include the index parameter in the Property statement. In this example, the test_number parameter is the index for the Scores property. Public Class Student ' The private array of scores. Private m_Scores(9) As Integer ' The indexed Score property procedures. Public Property Score(ByVal test_number As Integer) As _ Integer Get Return m_Scores(test_number) End Get Set(ByVal Value As Integer) m_Scores(test_number) = Value End Set End Property End Class
What is versioning in .NET?
main advantage of .net is versioning and solve very critical problem.
.net maintain one application with more then one version and also solve DLL HELL problem because it can run same application with different version at a same time [.Net have an Assembly. It gives the Portable Execution file.The main use of assembly is to maintain the Dll and exe’s.
So sometimes the programmer confused to which is modified code.That time the assembly provide the Version.
That is called versioning.
It is start from 1.0.*,…….]
What is DLL hell?
1.Adding of a new virtual method to a class exported from a DLL can cause the following problems: o If class already has a virtual method B and we are adding a new one named A before it, then we are changing the table of virtual methods. Now the first virtual method in the table will be A but not B and the client program which calls B will fail without recompilation as the call of B will cause the call of A and this is another method which possibly has other parameters and return type. o When a class doesn?t have virtual methods and none of its base classes have, then adding of a new virtual method to it or to its base class will cause adding of the pointer for the table of virtual methods. This will cause change in the class size. So the error will occur after a client program will allocate memory for the class (an amount of memory that was required before the class has been changed) and will try to modify some of the class' fields explicitly or implicitly. In this case, as the pointer to the table of virtual method is added to the beginning of the class, all addresses of the class fields are shifted and thus we will get an abnormal client program behavior or a runtime error. o In case when a class has virtual methods or any of its parent classes has, we can’t add virtual methods to classes exported from the DLL if they participate in the inheritance. We can?t add virtual methods not only to the beginning of the class declaration but also to the end of it. 1.The problem is in shifting in the table of virtual methods. Note that even if you add a new virtual method to the end of the class declaration then the child’s virtual methods will be shifted. 2.Adding of a new field (of any kind) to a class declaration can cause following problems: 1.Adding of a new field to the end of a class causes class size to change as in the case of adding of a virtual method to a class that didn?t have any. The client program will allocate less memory than it is required for a new class and this will cause referencing to the memory out of the class scope. 2.Adding of a new field between existing ones is even worse. It will case all addresses of fields after the new one to be shifted and a client application will work with the incorrect addresses while working with the fields that are situated after the new field. We also have the problem as in the previous point here.
How does you call and execute a SP in .NET?
Using command object we can execute a SP. Instead of sqlquery we have to pass the SP Name.
[command.connection =connectionstring
command.commandType=commandType.storedProcedure
command.commandtext=”sp_name”
command.executenonquery()]
Why Datareader is useful?
Data reader is useful when we just want to acccess datas from the database not when we want to perform DML operations. and It is useful when we want to perform forward only reading of datas.It wont requires any large volume of resources in the Front end.
[Datareader is read only or forward only. So it is very fast to fetch the data from database.]
What is the difference between Dataset and Recordset?
A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
A DataSet is designed to work without any continuing connection to the original data source.
Data in a DataSet is bulk-loaded, rather than being loaded on demand.
There’s no concept of cursor types in a DataSet.
DataSets have no current record pointer You can use For Each loops to move through the data.
You can store many edits in a DataSet, and write them to the original data source in a single operation.
Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
[1) With Data set you can retrive data from database like oracle and SQL Server and manage them in one dataset, with recordset this is not possible.
2) All representation of Dataset is using XML while recordset uses COM.
3) Recordset can not be transmitted on HTTP while Dataset can be.]
How does you get record no from 5 to 15 from a dataset of 100 records?
dim dRow as data.datarow for i as interger = 5 to 15 drow = dSet.Tables(0).Rows(i) 'process row next i
How do you declare static variable and how it is declared and what is its lifetime?
overloading——-having same method name with different signatures.
overriding——–methods name and signatures must be same.
[OverLoading : All the method will share the same name but it differes based on the parameter, type of parameter and number of parameter
Overriding : The method in the derived class the has the same name in the base class and it changes the behaviour or functionality of the method in the base class.]
What is shadowing?
When global and local varible in the same name.
the local varibale in a mehod or function which use to override the global is called the shadowing.
ie the Global varible is being shadowed by the local varible.
What is an abstract class?
It is a class which contains at least one abstract method (A method without any implementation). Other methods can have implementations. This class can not be instantiated. It can always become a base class for other classes.
What is the DIfference between Friend and Protected Friend?
Protected variable will be accessed in inherited class, but instance variable of class cant access protected variable. While friend variable will be accessed in inherited class as well as instance variable of class across the project. Where we need both functionality we are using protected friend scope. [Protected --> Accessible ONLY by 1.Derived classes 2.Within the same class Friend --> Accessible ONLY by 1.Derived classes 2.Classes in the same assembly 3.Within the same class Protected Friend --> Accessible ONLY by 1.Derived classes 2.Classes in the same assembly 3.Within the same class]
In order to get assembly info whcih namespace we should import?
system.reflection
ColumnMapping belongs to which namespaces?
System.Data.Common
Trace and Debug belongs to which namespaces?
system.process.diagnostics
What is the Difference between CLR & CTS?
CLR is the common language runtime. which is the feature makes the .net applications to run plantform independent langauge interoperability.
CTS Common type system is the part of the CLR which enable the Common Datatype system to All the .net languages. it also defines conventions to convert objects from one langauge to another.
What is CLR?
CLR means Common Language Runtime.It is Major component of the .NET frameworkIt provides number of benefits to the developers such as Exception handling,Security,Debugging and Versioning…
what is the root namespace for all types?
Imports system
What is the relation between Garbage collector and finalize and destructor?
here the GC calls an object’s FINALIZE method immediately before it collects an object that is no longer referred by the application GC doesn’t actually run finalize method when the GC finds a FINALIZE method it queues the obj up for the finalizer to execute the objects method [GC checks for those resources which are no longer used by the process. To release the memory from these resources and in order to regain the memory heap GC initiates destructors to destroy such instances of the program. Before the destructor void an instance variable finalize routine gets executed. This routine performs whatever is to be done before the object return to void state or prior to release of any unused resources.]
What are the similarities between class and structure?
Both can have constructors, methods, properties , fields,constants , enumerations, events and event handlers. Structure and class can implement interface. Both of them can have constructor without parameter and with parameter. Both can have delegates and events. [class is a collection of methods functions and properties enumerators and fields. structure can be defined as a tool for handling a group of logically related data item. the main difference is class is a referance type. structure is a reference value type.]
Do event have return type?
No. events do not have return type.
What do you mean by .Net Framework?
It is a collection of classes and services.It exists as a layer between.NET applications and underlying operating system.
i.e., it encapsulates the basic functionality that was earlier built into programming languages such as debugging and security services.
[.net framework is a collection of services & classes.it exists as a layer b/w .net applications 7 the underlying operating system.
.net framework consists of web forms,window forms & console applications that pertain to the presentation layer of the aaplication.
.net framework consists of two other components,the .net framework base classes & common language runtime(CLR).]
Is there any easy way to convert VB6 programs to VB.Net?
Just Open The Vb Project in Visual Studio.Net(File—> Open)
What is the Common Language Runtime?
CLR means commaon language runtime for the dot net frame work.
it is the frame work layer that resides above the operating system and handels/ manages the execution of the .net
applications.our .net programs don’t directly communicate with the operating system but through CLR.
OUT .NET APPLICATION—»CLR—>WINDOWS OS
What is VB.Net?
VB.NET has changed almost every aspect of Software development new concepts and techniques were intro the more imp thing is its a fully object oriented, new component techniques new visual tools for both local and internet interfaces.
How is VB.Net different from VB6?
VB6 was interpreter based language while VB.NET is a compiled language
VB6 was not a type-safe language while VB.NET is a type safe language.
VB6 used ?On Error Goto? syntax to handle exceptions at runtime. VB.NET uses the Try? Catch? Finally syntax to handle exceptions at runtime.
VB.NET has much enhanced object oriented support than VB6
VB6 does not allow developing the multithreaded applications. In VB.NET you can create multithreaded applications.
VB6 was only considered good for desktop windows application. In VB.NET you can also develop web applications, distributed applications,
create .NET windows and web controls and components, write windows and web services.
In VB.NET, you can also use reflections to read the meta-data of types and using reflection emit you can also generate code to define
and invoke types at runtime.
VB.NET uses .NET framework class library along with specialized VB library (System.VisualBasic) as a standard library. As a result,
the standard library for VB.NET is much enhanced and useful compared to VB6 standard library.
VB.NET is platform independent because of .Net framework. Programs written in VB.NET can run on any platform where .Net framework is present.
The platform include both hardware and software (operating system) platforms.
VB6 uses COM (Component Object Model) as component architecture. VB.NET uses assemblies as its component architecture. The Assemblies
architecture has removed a lot of problems with COM including DLL-Hell and versioning problem.
? Components created in VB6 (COM) need to make and update registry entries. VB.NET does not require any registry entry making the deployment
easier.
VB6 used ASP to build web applications. VB.NET uses ASP.NET to build web applications.
VB6 used ADODB and record-sets to implement data access applications. VB.NET uses ADO.NET and datasets to build data access applications.
The ADO.NET also supports the disconnected data access.
[1.VB6 was a scripting language while VB.NET is a Programming language
2.VB6 was supported Unstructured error handling by using On Error Gotos tatement.VB.NET supports structured exceptional by using Try…Catch…
Finally to handle exceptions at runtime.
3.VB.NET is completely supports object oriented features. but VB6 wont support
4.VB6 used ADO as Data access technology and record-sets to implement data access applications. Also here data transfer in the form of binary format.
VB.NET uses ADO.NET and datasets to build data access applications. The ADO.NET also supports the disconnected data access. Here the data transfer
in the form of xml format. So here their is faster data transfer.
5.Multiple versions are supported with vb.net but with vb6 its not supported
6.multithreading is supported with vb.net, but not with vb6]
what are Fixed memory leaks and threads locking problems?
Memory leak is a bug in the program which uses the memory continuously without releasing it until the system crash.
Thread locking problem is nothing but a deadlock situation in case of synchronous process when two consecutive threads get lock on a common resource and waiting for each other to release that. This happens usually in case when the semaphores or monitors are not used.
How to call a list box on the text if some one send me the code for it i understood the ?
like this what to do if we need to transfer the listbox items to the text if i am correct then my answer to this is double click on the listbox so that the eventof the listbox is displayed in the code editor
i. e private sub listbox1_selectedindexchanged……
textbox1. text=listbox1.selecteditem
What is the difference b/w Readonly Variable and Constant Variable?
variable used to store the data
Read only variable:-
Read only variable means read only but not allow to write
constant:
constant variable specify the constant value.
what is the dif b/w panel and groupbox?
Both panel and group box acts like a container to other controls they help us a lot in some applications where we want a group of controls or objects should be disabled or enabled when a specific task is performed the main difference isgroup box has a hording where u can place a
text of ure own whereas a panel is just like a frame what we used in VB but has a scrollbar(hs,vs)
What do you mean by ‘Option Strict On’ ?
Option Strict
Visual Basic language in general does not require explicit syntax to be used when performing operations that might not be optimally efficient (e.g. late binding) or that might fail at run time (e.g. narrowing conversions). This permissive semantics often prevents detection of coding errors and also affects the performance of the application.
VB.NET enables a programmer to enforce strict semantics by setting this option to “On”. When used, this option should appear before any other code.
This option can be set to “On” or “Off”. If this statement is not specified, by default, it is set to “Off”.
Syntax: Option Strict [On / Off]
When it is set to “On”, it disallows any narrowing conversions to occur without an explicit cast operator, late binding and does not let the programmer omit “As” clause in the declaration statement. Since setting it to “On” requires explicit conversion, it also requires that the
compiler be able to determine the type of each variable. Thus it is implied that Option Strict also means Option Explicit.
Visual Basic .NET allows implicit conversions of any data type to any other data type. However, data loss can occur if the value of one data type
is converted to a data type with less precision or a smaller capacity. Setting this option to “On” ensures compile-time notification of these types
of conversions so they may be avoided.
What are Jagged Arrays ?
a collection of discrete no of elements in each and every row is called as jagged arrays.
1)these jagged arrays doesn’t contain columns,
2)a jagged array also called as dynamic array
3)jagged array is a collection of dynamic arrays
4)these are faster and also save the memory.
syntax of jagged array:
int[][]x=new int [rows][]
here x is array name
What are Satellite Assemblies?
Satellite assemblies are user for localizing the applications resources. A satellite assembly is a DLL that contains only resource strings .we typically have one satellite assembly DLL for each language. Because these satellite assembly DLLs are separated from the main assembly (an .exe or DLL), it is easier to drop in 48 multi-language support as we progress in your development process.
How can we remove Handlers at Run time ?
RemoveHandler myobj.myEvent, AddressOf MyEventHandler
what is .net?
.Net is the Development Plateform which provides advanced feature facilities for the web and window application along with the window services.
The .Net is the Middle layer between the operating System and the .Net application .The feature of .Net that the .Net Component can talk with each other without worrying about the language in which they are originally.. Two main components are CLR stands for the common Language Runtime and the .Net FrameWork Base classes. The CLR performs the task of converting the IL to native code Which gives the .Net applications to be language Independent . The Other component Like .Net FramwWork Base Classes act as services to be provided to the .Net applications.
Can any body tell me the code procedure for preparing parameterized cristel reports?
the report should be generated by taking to or more parameters.
example: report should be genarated FROM DATE to TODATE?
We can generate Crystal Report by using date parameter, but the date format should be “yyyy,mm,dd”.
Ex. CrystaReport1.SelectionFormula = “{GLNOTE.L_DT} = date(“ & a & “)”
The variable ‘a’ should be assign with formated date
whats the difference bt. .dll extension and .exe extension files?
DLL : It is an inprocess server and runs in the same memory space as client application. Problem with dll is if any error comes in dll, whole application gets crashed.
Exe : It is an out of process server and rus as independent application in seperate memory. If error comes in exe, it does not affact the client application.
how can i extract the formated word(bold,italic,underline,font,color etc) from the msword file.?
using CommonDialog class
eg:
the code to invoke the default font dialog box by using the FontDialog control is given below:
private sub displayfont_click(byval sender as system.object,byval e assystem.eventargs) handles displayfont.click fontdialog.showDialog()
textbox1.font=fontdialog1.font
end sub
the code to invoke the default font dialog box by instantiating the fontdialog class is:
dim fdialog as new fontdialog()
private sub displayfont_click(byval sender as system.object,byval e as system.eventargs) handles displayfont.click
fdialog.showDialog()
textbox1.font=fontdialog1.font
end sub
Differences between VB.Net and C#, related to OOPS concepts?
- C# uses Must not Inherit, VB.Net uses sealed class
- C# uses Internal, VB.Net uses Friend
- VB.Net uses with events and end events
- C# uses abstract and VB.Net uses Must Inherit
Can u able to get the xml document in crystal report if yes how its possible?
Yes. You have to convert XML to dataset.
What is different between Web.Config and Machine.Config and Where it will be ?
The ASP.NET Web.config file is used to define the configuration settings for an ASP.NET application. ASP.NET and the .NET Framework use .config files to define all configuration options. The .config files, including the ASP.NET Web.config file, are XML files.
The ASP.NET application configuration settings can be changed by creating a file called Web.config and saving it in the root folder of the application.This is how the minimal Web.config file should look like:
The first line of the Web.config file is the same as the first line for any .config file and specifies that this is an XML document with utf-8 character encoding type.There are 2 important characteristics of the Web.config file. The first one is that if you change your Web.config file, you don?t need to re-compile your ASP.NET application.
The second one is that the Web.config file cannot be viewed in directly in a browser.
Server-wide configuration settings for the .NET Framework are defined in a file called Machine.config. The settings in the Machine.config file can be changed and those settings affect all .NET applications on the server.what if the Machine.config file defines different settings than the ones defined in your Web.config file? The settings in the Web.config file override the settings in the Machine.config file.
[A web.config file is used to configure one asp .net web application. Each Asp.net application has a web.config file. A Machine.config file is used to configure the applications in a particular machine. Configuration done in machine.config file is affected on any application that runs on a particular machine. ]
How to store and retrieve images in sql server database through VB.NET?
To store image in database 1st u need to make table like this
CREATE TABLE PicImage
(
Picid int,
Pic Image
)
Now in vb.net coding u have to write code like this
Dim ms As New MemoryStream
pic_photo.Image.Save(ms, pic_photo.Image.RawFormat)
arrImage = ms.GetBuffer
ms.Flush()Now pass arrImage in ur insert query.
