1.It is useful for enabling access to commands in a variety of contextual situations

2.It is created using ContextMenu control.

3.It is created at run time in the same manner as main menus

Command builder generates insert/update/delete commands for data adapter based on select command. Automatic creation of insert/update/delete commands hinders performance. The command builder uses select command property of data adapter to determine values for other commands.

 

It is member of the class which can be access without creating instance of the class. It belongs to the class and not to the instance of the class.

 

Visual inheritance allows deriving forms from the base form with common controls.

 

It provides additional features to the controls. ErrorProvider, HelpProvider, and ToolTip components are the examples of extender provider.  

 

Managed code not always is slower than unmanaged code. In managed code, the CLR does some optimization for the way loops, subroutines should run and what is the best way to execute it.

 

when you want to use your application should run in differnet language like you have developed the application for english and should also run in dutch, french, japanese etc., then through globalization you can set lacal and culture for the each language in seperate folder. So that when the application will run for a specific region it will be show the content in same language.

 

A Dataset may contain multiple tables. The DataViewManager is a single object that manages all the DataViews. It can be used to view settings for all the tables in a DataSet.You could use it to bind multiple tables in a control such as a parent-child relationship. The DataViewManager has a collection of DataViewSetting objects, each for a table in DataSet.Then you can even specify the default sort, filters etc in each of the DataViewSetting

 

Dataset

1.DataSet object can contain multiple rowsets from the same data source as well as from the relationships between them

2.Dataset is a disconnected architecture

3.Dataset can persist data.

Datareader

1.DataReader provides forward-only and read-only access to data.

2.Datareader is connected architecture

3.Datareader can not persist data.

 

Stored procedures normally are faster as they have a predictable execution plan. Therefore, if a stored procedure is being executed for the second time, the database gets the cached execution plan to execute the stored procedure. LINQ supports type safety against stored procedures.

 

Field-level validation means validating each field as it receives focus. Form-level validation is the process where you validate all data on a form before form is submitted.

 

You can provide validation code with properties that validate data being read or set. You can not add any validation code while using fields.

 

A delegate acts like a strongly typed function pointer. Delegates can invoke the methods that they reference without making explicit calls to those methods.

 

Parse method is used to convert string value to numeric type. All numeric data type have a Parse method.

 

Trace produces messages about program conditions even after application is compiled and released without interrupting application execution.

 

The Try block encapsulate set of code that is error prone and can throw exception. If an exception is thrown, it can be caught in an appropriate Catch (catch) block. You have Finally block that can contain code that must be executed even if no exception is handled.

 

Data Provider is a set of components that facilitate data access. It contains components like connection, command, dataReader, dataAdapter. Connection object connects to the data source. Command object represents a direct command to the data source. DataReader object that provides connected, forward-only, read-only access to a database. DataAdapter that provides disconnected data access.

 

DataReader: It is lightweight class that provides connected and forward-only data access. It uses connection object exclusively. You can read data; you can’t modify data using DataReader.

DataAdapter: This class provides disconnected data access. It opens a data connection just long enough to retrieve the data, and loads the data into a DataSet, thus provides in-memory copy of the data.

 

The preserve keyword helps to prevent data in an array from being lost.

 

XML serialization has some limitations. It converts public property values and fields, but does not encode type information. Also it does not encode private properties and fields, which requires binary serialization. Any class to be serialized to XML must have a public, parameterless constructor. One advantage of XML serialization is that the serialized data, being XML, rarely has any problems passing over networks and through security measures, such as firewalls, that might be unhappy with a binary data stream. For this reason, XML serialization is used by .Net Web services. Another advantage is that XML serialization is not platform-specific. In other words, you do not have to have .Net or Windows on both ends of the process.

 

string class in immutable. Immutable is nothing but the value assigned to string cannot be changed. Stringbuilder class is mutable. mutable is nothing but the value assigned to stringbuilder can be changed.

 

An Assembly is the building block of a VB.NET application. An Assembly is a complied and versioned collection of code and metadata. Once complete forms an atomic functional unit.

 

One should create a resource only assembly if you need to update the resources frequently without recompiling the whole solution.

Steps to create it are:

a. Create a new empty project.

b. Add a new resource item to the project.

c. In project's property pages, choose output type as class library..

d. Build project to have the resource files being compiled in an assembly.

 

1.Show next statement

2.step into

3.step over

4.step out

 

Addhandler associates an event with its handler at runtime.

 

SystemExceptions are thrown by the CLR and are of more generic nature, whereas, ApplicationExceptions are thrown by Applications. Therefore when creating a custom Exception class we should only inherit it from Application Exception and not SystemException.

 

Console Applications have only recently been introduced in VB (Excluding VB for DOS). They are command line based and run in within a DOS Shell (DOS Window). Unlike Windows Applications, Console Applications do not support Windows GUI's. Which means that you can't work with controls from the toolbox.

 

Enumerations are new in VB.Net (As apposed to VB(i)) and they are used to group related sets of constants. To create a Enumeration you use the Enum statement.

 

Delegates are used to work with the address of procedures. This is much like pointers in C and C++. Sometimes it's useful to pass the location of a procedure to other procedures.

 

The System.Environment namespace includes the functionality to get the environment information such as the UserName and OS Version.

 

To convert the format of an image you need to use the System.Drawing namespace. Using this code you can convert to a variety of graphic file formats, such as GIF or JPG.

 

Indexed properties, for example, the DeviceName property in TwainControlX, are not directly supported in VB.NET. These properties become hidden when the control is wrapped for use in the .NET environment. This problem is easily solved by prefixing the property name with either 'get_' or 'set_' depending whether the property is being read or written.

 

Destructors are used to de-allocate resources i.e. to clean up after an object is no longer available.

 

To run a .EXE file from a VB.NET application you need to import the System.Diagnostics namespace.

 

This error is usually caused by adding the control dynamically in code instead of placing an instance of the control on a form at design time. If the control instance must be created dynamically, the licence information must be added in the code.

 

you can use the classes and methods in System.Diagnostics.Process to accomplish these tasks and more.

 

In Visual Basic .NET there are two main ways to achieve this result, the DateDiff function or through the TimeSpan structure.

 

You can run them both on the same machine.

 

To retrieve information from the configuration file.

Create an instance of AppSettingsReader to read the configuration file.

Call the GetValue method to read values represented in the configuration file.

To add configuration file entries

Create elements in the node of the configuration file.

Specify a value for the entry and a key in the element.

 

Imperative security is implemented by calling methods of Permission objects in code at run time. Declarative security is configured by attaching attributes representing permissions to classes and methods. Additionally, you can request assembly-wide permissions using the Assembly (assembly) directive with declarative security.  

 

A bootstrapper application automatically detects if Windows Installer is installed on the target machine. If Windows Installer is not present, it installs Windows Installer before proceeding with the rest of the installation.

 

Break mode allows reading code line-by-line. You can observe code in Break mode by using Step Into, Step Over, Step Out, Run To Cursor, and Set Next Statement.  

 

An abstract class is a class that cannot be instantiated but must be inherited. It can contain both implemented methods and abstract methods.

 

Keyboard events allow you to validate keystrokes. They are raised by the control that has the focus and is receiving input. Following are the keyboard events.

1. KeyDown

2. KeyUp

3. KeyPress

 

A value type holds the data assigned to it. A reference type contains the pointer i.e. memory address that holds the data.

 

Both the class and structure are user define types. 

Both are the template of the object. 

Both contain members like methods, properties, fields and use contractor for initialization. 

Both of them inherit from System.Object.

The greatest change in VB6 and VB.NET is of runtime environment. VB6 used the VB-Runtime while VB.NET uses the .Net Common Language Runtime (.Net CLR). The CLR is much better designed and implemented than VB-Runtime. The CLR uses better code translation through Just in Time compiler while VB-Runtime interprets the code. The CLR Garbage Collector is also more efficient than VB6 one as it may detect cyclic references too.

It is a method that is executed when an object is garbage collected. It is similar in function to a destructor. It keeps the memory managed by taking appropriate an action against an object that is released or is no longer in use. It is called up internally on garbage collection.

 

Implicit cast allows conversion without any loss of data and it takes place only when there is no possible of loss of data. When there is any possibility of loss of data, explicit cast is required. Remember, explicit cast if not applied properly can result a loss of data precision.