Vb-Net-Ado

VB.NET2005

What is a Program?

An organized list of instructions that, when executed,

causes the computer to behave in a predetermined

manner. Without programs, computers are useless.

A program is like a recipe. It contains a list of ingredients

(called variables) and a list of directions

(called statements) that tell the computer what to do with

the variables. The variables can represent

numeric data, text, or graphical images.

A programming language is an artificial

language that can be used to control the

behavior of a computer.

Source code is any series of statements written

in a programming language.

Computer Programming is the art of making a computer

do what you want it to do.(often shortened to programming

or coding) is the process of

writing, testing, and maintaining the source code

of computer programs.

What is Programming?

Event-driven Programming

In computer programming, Event-Driven

programming or event-based programming is a

programming paradigm in which the flow of the

program is determined by events

Ex:

sensor outputs or user actions (mouse clicks, key

presses) or messages from other programs or threads.

Object-oriented programming

Object-oriented programming (OOP) is a programming

model that uses "objects" – data structures consisting of data

fields and methods – and their interactions to design

applications and computer programs.

Programming techniques may include features such as,

1. Information hiding,

2. data abstraction,

3. encapsulation,

4. modularity,

5. polymorphism, and inheritance.

It was not commonly used in mainstream software application

development until the early 1990s. Many modern programming

languages now support OOP.

Why Object oriented approach?

A major factor in the invention of Object-Oriented approach is to remove some

of the flaws encountered with the procedural approach. In OOP, data is treated

as a critical element and does not allow it to flow freely. It bounds data closely

to the functions that operate on it and protects it from accidental modification

from outside functions. OOP allows decomposition of a problem into a number

of entities called objects and then builds data and functions around these

objects.

A major advantage of OOP is code reusability.

Some important features of Object Oriented programming are as follows:

• Emphasis on data rather than procedure

• Programs are divided into Objects

• Data is hidden and cannot be accessed by external functions

• Objects can communicate with each other through functions

• New data and functions can be easily added whenever necessary

• Follows bottom-up approach

Concepts of OOP:

1. Objects

2. Classes

3. Data Abstraction and

Encapsulation

4. Inheritance

5. Polymorphism

Objects

Objects are the basic run-time entities in an object-oriented system.

Programming problem is analyzed in terms of objects and nature of

communication between them. When a program is executed, objects

interact with each other by sending messages. Different objects can

also interact with each other without knowing the details of their data

or code.Dog(Object)

Attributes

• Skin color

• Eye color

• Height

• Weight

• Etc….

Behaviors

• Eat

• Bark

• Run

• Jump

• Etc….

Classes

A class is a collection of objects of similar type. Once a

class is defined, any number of objects can be created

which belong to that class.

MALE

SON

FATHER

Data Abstraction and Encapsulation

Abstraction refers to the act of representing essential features without

including the background details or explanations. Classes use the

concept of abstraction and are defined as a list of abstract attributes.

Storing data and functions in a single unit (class) is encapsulation.

Data cannot be accessible to the outside world and only those

functions which are stored in the class can access it.

ENCAPSULED

Formula + ingredients+

methods+ etc….

Inheritance

Inheritance is the process by which objects can acquire the properties of

objects of other class. In OOP, inheritance provides reusability, like, adding

additional features to an existing class without modifying it. This is

achieved by deriving a new class from the existing one. The new class will

have combined features of both the classes.

Polymorphism

Polymorphism means the ability to take more than one form. An

operation may exhibit different behaviors in different instances.

The behavior depends on the data types used in the operation.

Polymorphism is extensively used in implementing Inheritance.

Shape

Triangle

Rectangle

Software Development Life Cycle

(SDLC)

A software development process is a structure

imposed on the development of a software product.

Synonyms include software life cycle and software

process. There are several models for such

processes, each describing approaches to a variety

of tasks or activities that take place during the

process.

SDLC is the Process of Developing

information system through Investigation,

Analysis, Design, Implementation and

maintenance

Software development life cycle model is also called as waterfall

model which is followed by majority of systems. This software

development life cycle process has the following seven stages in it

namely

1. System Requirements Analysis

2. Feasibility study

3. Systems Analysis and Design

4. Code Generation

5. Testing

6. Maintenance

7. Implementation

1. System Requirements Analysis:

The first essential or vital thing required for any software development is system. Also the system requirement may vary based on the software product that is going to get developed. So a careful analysis has to be made about the system requirement needed for the development of the product. After the analysis and design of the system requirement phase the system required for the development would be complete and the concentration can be on the software development process.

2. Feasibility study:

After making an analysis in the system requirement the next step is to make analysis of the software requirement. In other words feasibility study is also called as software requirement analysis. In this phase development team has to make communication with customers and make analysis of their requirement and analyze the system. By making analysis this way it would be possible to make a report of identified area of problem. By making a detailed analysis on this area a detailed document or report is prepared in this phase which has details like project plan or schedule of the project, the cost estimated for developing and executing the system, target dates for each phase of delivery of system developed and so on. This phase is the base of software development process since further steps taken in software development life cycle would be based on the analysis made on this phase and so careful analysis has to be made in this phase.

3. Systems Analysis and Design:

This is an important phase in system development .Here analysis is made on the design of

the system that is going to be developed. In other words database design, the design of the

architecture chosen, functional specification design, low level design documents, high level

design documents and so on takes place. Care must be taken to prepare these design

documents because the next phases namely the development phase is based on these

design documents. If a well structured and analyzed design document is prepared it would

reduce the time taken in the coming steps namely development and testing phases of the

software development life cycle.

4. Code Generation:

This is the phase where actual development of the system takes place. That is based on the

design documents prepared in the earlier phase code is written in the programming

technology chosen. After the code is developed generation of code also takes place in this

phase. In other words the code is converted into executable in this phase after code

generation.

5. Testing:

A software or system which is not tested would be of poor quality. This is because this is the phase where system developed would be tested and reports are prepared about bugs or errors in system. To do this testing phase there are different levels and methods of testing like unit testing, system test and so on. Based on the need the testing methods are chosen and reports are prepared about bugs. After this process the system again goes to development phase for correction of errors and again tested. This process continues until the system is found to be error free. To ease the testing process debuggers or testing tools are also available.

6. Maintenance:

After the testing phase is completely through and the system is found to be error free it is delivered to the customer. But no real system would be error free even then. This is because when the system gets executed in real user system scenarios there would be possibilities of lot of bugs and errors. This phase is called the maintenance phase and the errors in this are recorded and changes has to be made in the system accordingly and again testing phase comes into picture.

7. Implementation:

This is the final stage when the system gets into live.

The above software development process are all vital for a

system to get developed with quality and thus to

achieve customer satisfaction which is the main objective of

any software development process.

Objects

An object is an entity which has a state and a defined set

of operations which operate on that state. The state is

represented as a set of object attributes. The operations

associated with the object provide services to other

objects (clients) which request these services when some

computation is required.

Objects are created according to some object class

definition. An object class definition serves as a template

for objects. It includes declarations of all the attributes and

services which should be associated with an object of that

class.

Objects and object classes

• Objects are entities in a software system

which represent instances of real-world

and system entities

• Object classes are templates for objects.

They may be used to create objects

• Object classes may inherit attributes and

services from other object classes

Introduction

The .NET Platform provides the foundation for the next

generation of software that connect disparate systems,

information, devices, & users in a more unified and

professionalized way. It includes web services(XML) that

enables different Technologies to interoperate. It provides

software developers the tools and technology to quickly and

efficiently deliver business solutions that span multiple

applications and multiple client devices across many

organizations. It enables user to control how, when, and what

information is delivered to them.

What is the .NET Platform?

The .NET Framework is a set

of programming services

designed to simplify

application development in

the highly distributed

environment of the Internet.

The .NET Framework has

two main components : the

common language runtime

and the class library

How the .NET Framework Works

Terms & Definitions

Class - A Class is a named programming entity that comprise a common set of

methods, properties, and attributes. For Example, Form is one of the classes in

the System.Windows.Forms namespace that used to create Windows Forms

Namespace – A namespace identifies a collection of related classes and/or other

namespaces in the .NET Framework. Examples of namespaces are

System.Windows.Forms

Class library – The class library is a comprehensive object-oriented collection of

reusable classes that are organized by their functionality into hierarchical

namespaces.

Common Language Runtime – the common language runtime is the foundation

of the .NET Framework. In the .NET environment , programmers develop

applications in the .NET compatible language of their choice, the code is compiled

in to MSIL(Microsoft Intermediate language) and the runtime manages and runs

the compiled code.

Visual Studio .NET Integrated Development

Environment (IDE)

Menu

bar

Solution

Explorer

Property

WindowTool Box

The Form Window is central to developing Visual Basic applications.

It is where you draw your application.

The Toolbox is the selection menu

for controls used in your

application.

The Properties Window is used to

establish initial property values for

objects. The drop-down box at the top of

the window lists all objects in the current

form. Two views are available:

Alphabetic and Categorized. Under this

box are the available properties for the

currently selected object

Solution Explorer provides you with an

organized view of your projects and their

files as well as ready access to the

commands that pertain to them. A toolbar

associated with this window offers

commonly used commands for the item

you highlight in the list. To access Solution

Explorer, select Solution Explorer on the

View menu.

Class name list Method name list

Code editor allows user to write and maintain the code related to the

solution

Structure of a Visual Basic Application

Application (Project) is made up of:

Forms - Windows that you create for user interface

Controls - Graphical features drawn on forms to allow user interaction

(text boxes, labels, scroll bars, command buttons, etc.) (Forms and

Controls are objects.)

Properties - Every characteristic of a form or control is specified by a

property. Example properties include names, captions, size, color,

position, and contents. Visual Basic applies default properties. You

can change properties at design time or run time.

Methods - Built-in procedure that can be invoked to impart some

action to a particular object.

Event Procedures - Code related to some object. This is the code

that is executed when a certain event occurs.

General Procedures - Code not related to objects. This code must be

I invoked by the application.

Modules - Collection of general procedures, variable declarations, and

constant definitions used by application.

Steps in Developing Application

There are three primary steps involved in

building a Visual Basic application:

1. Draw the user interface

2. Assign properties to controls

3. Attach code to controls

Naming Objects

Control type prefix Example

Check box chk chkReadOnly

Combo box, drop-down list box cbo cboEnglish

Command button cmd cmdExit

Form frm frmEntry

Label lbl lblHelpMessage

List box lst lstPolicyCodes

ListView lvw lvwHeadings

Option button opt optGender

Picture box pic picVGA

RichTextBox rtf rtfReport

Text box txt txtLastName

Timer tmr tmrAlarm

Visual Basic Language

Keywords

The following table contains a listing of the Visual Basic .NET language

keywords. All language keywords are reserved.

AddHandler AddressOf Alias And

AndAlso Ansi As Assembly

Auto Boolean ByRef Byte

ByVal Call Case Catch

CBool CByte CChar CDate

CDec CDbl Char CInt

Class CLng CObj Const

CShort CSng CStr CType

Date Decimal Declare Default

Delegate Dim DirectCast Do

Double Each Else ElseIf

End Enum Erase Error

Event Exit False Finally

For Friend Function Get

GetType GoSub GoTo Handles

If Implements Imports In

Inherits Integer Interface Is

Let Lib Like Long

Loop Me Mod Module

MustInherit MustOverride MyBase MyClass

Namespace New Next Not

Nothing NotInheritable NotOverridable Object

On Option Optional Or

OrElse Overloads Overridable Overrides

ParamArray Preserve Private Property

Protected Public RaiseEvent ReadOnly

ReDim REM RemoveHandler Resume

Return Select Set Shadows

Shared Short Single Static

Step Stop String Structure

Sub SyncLock Then Throw

To True Try TypeOf

Unicode Until Variant When

While With WithEvents WriteOnly

Xor #Const #ExternalSource #If...Then...#Else

#Region - & &=

* *= / /=

\ \= ^ ^=

+ += = -=

Variables

With Visual Basic, and most programming languages, what you are doing is

storing things in the computer's memory, and manipulating this store. If you

want to add two numbers together, you put the numbers into storage areas

and "tell" Visual Basic to add them up. But you can't do this without variables.

1. No more than 40 characters

2. They may include letters, numbers, and underscore

(_)

3. The first character must be a letter

4. You cannot use a reserved word (word needed by

Visual Basic)

Dim

Short for Dimension. It's a type of variable. You declare (or "tell" Visual

Basic) that you are setting up a variable with this word.

number1

This is a variable. In other words, our storage area. After the Dim word,

Visual Basic is looking for the name of your variable. You can call your

variable almost anything you like

As Integer

We're telling Visual Basic that the variable is going to be a number

(integer).

Number1 = 3

The equals sign is not actually an equals sign. The = sign means assign a

value of. In other words, here is where you put something in your variable.

We're telling Visual Basic to assign a value of 3 to the variable called

number1.

Now examine this:

Dim number1 As Integer

Dim number 2 As Integer

number1 = 3

number2 = 5

Data Type Size in Bytes Description

Byte 1 8-bit unsigned integer

Char 2 16-bit Unicode characters

Integer 4 32-bit signed integer

Double 8 64-bit floating point variable

Long 8 64-bit signed integer

Short 2 16-bit signed integer

Single 4 32-bit floating point variable

String Varies Non-Numeric Type

Date 8

Boolean 2 Non-Numeric Type

Object 4 Non-Numeric Type

Decimal 16 128-bit floating point variable

Data Types in VB .NET

Visual Basic Data Types

Data Type

Boolean

Integer

Long (Integer)

Single (Floating)

Double (Floating)

Currency

Date

Object

String

Variant

Suffix

None

%

&

!

#

@

None

None

$

None

There are three ways for a variable to be typed (declared):

1. Default

2. Implicit

3. Explicit

If variables are not implicitly or explicitly typed, they are assigned the variant

type

by default. The variant data type is a special type used by Visual Basic that

can contain numeric, string, or date data.

To implicitly type a variable, use the corresponding suffix shown above in

the data type table. For example,

Dim <Variable name> $ = "This is a string"

//creates a string variable, while

Dim <Variable name> % = 300

//creates an integer variable.

Variable Declaration

There are many advantages to explicitly typing variables. Primarily, we insure

all computations are properly done, mistyped variable names are easily spotted,

and Visual Basic will take care of insuring consistency in upper and lower case

letters used in variable names. Because of these advantages, and because it is

good programming practice, we will explicitly type all variables.

To explicitly type a variable, you must first determine its scope.

There are four levels of scope:

1. Procedure level

2. Procedure level, static

3. Form and module level

4. Global level

Within a procedure, variables are declared using the Dim statement:

Dim <Variable name> as Integer

Dim <Variable name> as Double

Dim <Variable name> , <Variable name> as String

Procedure level variables declared in this manner do not retain their value once

a procedure terminates.

To make a procedure level variable retain its value upon exiting the procedure,

replace the Dim keyword with Static:

Static <Variable name> as Integer

Static <Variable name> as Double

Form (module) level variables retain their value and are available to all

procedures within that form (module). Form (module) level variables are

declared in the declarations part of the general object in the form„s (module's)

code window.

The Dim keyword is used:

Dim <Variable name> as Integer

Dim <Variable name> as Date

Public level variables retain their value and are available to all procedures within

an application. Module level variables are declared in the declarations part of the

general object of a module's code window. (It is advisable to keep all Public

variables in one module.) Use the Public keyword:

Public <Variable name> as Integer

Public <Variable name> as Date

String Variables

What is a String? Actually a string is nothing more than text. And if we want

Visual Basic to store text we need to use the word "String". To set up a variable

to hold text we need to use As String and not As Integer. If the information we

want to store in our variables is a First Name and a Last Name, we can set up

two variables like this.

Dim FirstName As String

Dim LastName As String

Arrays

An array is a collection of values of the same data type. The values in an array are called

array elements. Array elements are accessed using a single name and an index number

representing the position of the element within the array.

An array is a standard structure for storing data in any programming language. Variables can

hold single entities, such as one number, one date, or one string and arrays can hold sets of

data of the same type (a set of numbers, a series of dates, and so on). An array has a name,

and the values stored in it can be accessed by an index.

Declaring Arrays

Unlike simple variables, arrays must be declared with the Dim (or

Public, or Private) statement followed by the name of the array and the

index of the last element in the array in parentheses for example:

Dim Ages(19) As Integer

Initializing Arrays

Just as we can initialize variables in the same line where we declare them, we

can initialize arrays too, with the following constructor:

Here´s an example that initializes an array of strings:

Dim names() As String ("john", "Sam","Hedric")

This statement is equivalent to the following statements, which declare an array

with two elements and then set their values:

Dim names(2) As String

names(O)="John"

names(1) ="Sam"

names(2) ="Hedric"

The number of elements in the curly brackets following the array´s declaration

determines the dimensions of the array, and we can´t add new elements to the

array without resizing it.

Multidimensional Arrays

Arrays can be multidimensional. Multidimensional arrays can be thought of as arrays-of-

arrays. For example, to visualize a two dimensional array we could picture a row of CD

racks. To make things easier, we can imagine that each CD rack could be for a different

artist. Like the CDs, the racks would be identifiable by number. Below we'll define a two

dimensional array representing a row of CD racks. The strings inside of the array will

represent album titles.

' Here we will define an array where the first dimension contains 2 elements and the

second dimension contains 4 elements

Dim cdRack(1,3) As String

' A CD rack for the Beatles

cdRack(0, 0) = "Rubber Soul"

cdRack(0, 1) = "Revolver"

cdRack(0, 2) = "The White Album"

cdRack(0, 3) = "Let It Be“

' A CD rack for the Rolling Stones

cdRack(1, 0) = "Sticky Fingers"

cdRack(1, 1) = "Beggars Banquet"

cdRack(1, 2) = "Let It Bleed"

cdRack(1, 3) = "Tattoo You"

0 1 2 3

0 Rubber Soul RevolverThe White

AlbumLet It Be

1Stickey

Fingers

Beggars

BanquetLet It Bleed Tatto You

Operators

Visual Basic comes with many built-in operators that allow us to manipulate data.

An operator performs a function on one or more operands.

For example, we add two variables with the "+" addition operator and store the

result in a third variable with the "=" assignment operator like this:

int x + int y = int z.

The two variables (x ,y) are called operands. There are different types of

operators in Visual Basic

1. Arithmetic Operators

2. Concatenation Operators

3. Comparison Operators

4. Logical / Bitwise Operators

Operators

Operator Use

^ Exponentiation

-Negation (used to reverse the sign of the

given value, exp -intValue)

* Multiplication

/ Division

\ Integer Division

Mod Modulus Arithmetic

+ Addition

- Subtraction

Arithmetic Operators

Arithmetic operators are used to perform arithmetic operations that involve

calculation of numeric values. The table below summarizes them:

Dim x, y, z As Integer

x = 30

y = 20

z = x + y

MessageBox.Show(z)

z = x - y

MessageBox.Show(z)

z = x * y

MessageBox.Show(z)

z = x / y

MessageBox.Show(z)

Example

Operator Use

+ String Concatenation

& String Concatenation

Concatenation Operators

Concatenation operators join multiple strings into a single string. There are two

concatenation operators, + and & as summarized below:

Example:

Dim str1, str2, str3, str4 As String

str1 = "Concatenation"

str2 = "Operators"

str3 = str1 + str2

MessageBox.Show(str3)

str4 = str1 & str2

MessageBox.Show(str4)

Operator Use

= Equality

<> Inequality

< Less than

> Greater than

>= Greater than or equal to

<= Less than or equal to

Comparison Operators

A comparison operator compares operands and returns a logical

value based on whether the comparison is true or not. The table

below summarizes them:

Dim x, y As Integer

x = 10

y = 15

If x = y Then

MessageBox.Show ("x is Equal to y")

ElseIf x < y Then

MessageBox.Show("x is less than y")

ElseIf x > y Then

MessageBox.Show("x is greater than y")

End If

Example

Operator Use

Not Negation

And Conjunction

AndAlso Conjunction

Or Disjunction

OrElse Disjunction

Xor Disjunction

Logical / Bitwise Operators

The logical operators compare Boolean expressions and return a Boolean

result. In short, logical operators are expressions which return a true or false

result over a conditional expression. The table below summarizes them:

The Not operator

The Not operator will return the opposite of the Boolean value, Not True will return False and

Not False will return True. See the example below:

Dim P As Boolean = False

MessageBox.Show(Not P)

The And operator

The And operator will check if two boolean values are true. Both needs to True or the And

operator won't return true. See the examples below:

Dim P, Q As Boolean

P = True

Q = False

MessageBox.Show(P And Q)

The Or operator

For the Or operator to return True, at least one of the values have to be True. If both are True

doesn't matter, it will also return True. Look at this example below:

Dim P, Q As Boolean

P = True

Q = False

MessageBox.Show(P Or Q)

The Xor operator

The Xor operator will return True if and only if one of the values are True. This means that the

different between Or and Xor is that if both values are True, Or will return True but Xor will

return False, See this example:

Dim P, Q As Boolean

P = False

Q = False

MessageBox.Show(P Xor Q)

Console Applications

Console Applications are command-line oriented applications that allow us to read characters from the

console, write characters to the console and are executed in the DOS version. Console Applications are

written in code and are supported by the System.Console namespace.

Example on a Console Application

Module Module1

Sub Main()

System.Console.Write("Welcome to Console Applications")

End Sub

End Module

The following code is example of a console application:

Run the code by selecting Debug->Start or Press Ctrl+F5

Commenting the Code

Comments in VB.NET begin with a single quote (') character and the

statements following that are ignored by the compiler. Comments are

generally used to specify what is going on in the program and also gives an

idea about the flow of the program. The general form looks like this:

'declaring an integer

Dim I as Integer

Breaking the Code to understand it

Visual Basic Module and Modules are designed to hold code. All the code

which we write should be within the Module.

Next line starts with Sub Main(), the entry point of the program.

The third line indicates that we are using the Write method of the

System.Console class to write to the console.

A function is a segment of code that accepts zero, one or more arguments and

returns a single result. Some

perform basic mathematical tasks. Others manipulate string data such as

converting text to uppercase or lowercase letters.

What is a Function ?

What is an Argument ?

An argument is a value you pass to a function so the function has data to

work with . Function names have parentheses at the end to hold the

function arguments. Even if a function has no arguments, the parenthesis

are required. Two intrinsic functions include message boxes and input

boxes

Selection Structure?

The If Then statement(or only If Statement) is a block of code that will

only be run if the specific condition is met and therefor will return True,

if the condition returns False the code will jump past the If block and

continue at "End If" which is the end of an If block. The syntax for and If

statement are:

If <condition> Then

'code to be executed if the condition are met

End If

If True Then

MessageBox.Show("Inside the If block")

End If

The If statement check if the condition is True, and here it is. This will

make the line(s) inside the If block to be executed. In this example a

messagebox will be shown. But if we change "True" to "False" in the

above code, the messagebox will not be showed since the code will

jump past the If block because the conditions where False.

Example

Dim x As Integer

x = 3

If x > 0 Then

MessageBox.Show("x is greater then 0")

End If

If Then Else Statement:

The opportunities doesn't end there. We can also create something called an If Then Else

statement. This works like an If Then Statement but it has two blocks of codes. If the condition

is met(True) the first block of code will be run. But instead of just jumping to the End If straight

away if the conditions aren't met(False) the second block of code is executed.

The syntax for an If Then Else Statement looks like this:

Code:

If <condition> Then


Else

'code to be executed if the condition are NOT met

End If


x = 1

y = 9

z = 14

If x < y And y < z Then

MessageBox.Show("x is smallest and z is largest")

Else

MessageBox.Show("The variables are not in size order")

End If

Example

If Then ElseIf Else Statement:

The ElseIf blocks is working exactly the same as an If block, the If block is the first one and then

it's followed by ElseIf blocks and at the end you can add a else block if you want. If the If block's

statement are True that block will be run and then the code will jump to the End If, however if it's

False it will test if the condition of the first ElseIf block is True, if this also is False it will go to the

second one etc. If all conditions are False and there's an Else block this will be executed.

Here's the syntax for the If Then ElseIf Else Statement:

If <condition> Then


ElseIf <condition> Then

'code to be executed if the condition are met but no conditions above

Else

'code to be executed if none of the conditions are met

End If

Example


x = 2

y = 5

z = 8

If x = 0 Then

MessageBox.Show("x is equals to 0")

ElseIf x < y And y < z Then

MessageBox.Show("x is smallest and z is largest")

ElseIf x = y And y = z Then

MessageBox.Show("all variables has the same value")

Else

MessageBox.Show("None of the conditions above are met")

End If

The select case statement is good to use when you want different blocks of code to be

executed depending on different values on one variable. If statements is good if you only

need to test one value

Anyway, to use a select case statement you have to create it by writing "Select Case" and

then the value you want to test. End the statement with "End Select". Could look something

like this:

Select Statement

Select Case <Value that intended to test>

End Select

Select Case myVariable

Case 1

MessageBox.Show("myVariable = 1")

Case 2


Case 3, 4

MessageBox.Show("myVariable = 3 or 4")

Case 5


Case Else

MessageBox.Show("myVariable is nether 1,2,3,4 or 5")

End Select

Example

More advanced Select Case Statements

To

When using some sort of values(Integers for example) you can add a whole

range of numbers to one case by using "[number] To [number]", like this:


Case 0 To 5

MessageBox.Show("myVariable is

between 0 and 5")

Case 6 To 10


between 6 and 10")

Case 11


End Select

Is

You can also add relational operators to your select case statement. Do this by replace

"Case [value]" with "Case Is [relational operator] [value]". Actually a select case statement

does always contains a relational operator, the is equals to operator (=) even though it's

hidden. This means that "Case Is = myValue" is the same as "Case myValue". Here comes

a little example on how to use it:


Case Is > 0


greater then 0")

Case Is < 0

MessageBox.Show("myVariable is less

then 0")

Case Else


equals to 0")

End Select

Exercise

Part 1 - If statements

Start a new project. Add a textbox, a Label and a button to your new Form. Then write a programme that does the following: 1. Asks users to enter a number between 10 and 20. 2. The number will be entered into the Textbox. 3. When the Button is clicked, your Visual Basic code will check the number entered in the Textbox. 4. If it is between 10 and 20, then a message will be displayed. 5. The message box will display the number from the Textbox. 6. If the number entered is not between 10 and 20 then the user will be invited to try again, and whatever was entered in the Textbox will be erased

Part 2 - Select Case Statements

Add a Combo box and another button to your form. Create a list of items for your Combo Box. The list of items in your Combo box can be anything you like - pop groups, football teams, and favorite foods, anything of your choice. Then try the following: Use a select case statement to test what a user has chosen from your drop-down list. Give the user a suitable message when the button was clicked.

Looping Structure

The While Loop:

The while loop will continue with its loop as long a condition remains True. The

condition is tested at the beginning each time the loop will start a new turn. If the

condition isn't met at the beginning the loop won't even run once. The syntax of a

while loop looks as following:

Code:

While <condition>

'Code that will be run once per turn

End While

To show a simple example:

Dim X as Integer = 3

While X<300

X*=2

End While

Do While loop:

This type of loop has only one difference to the While loop more then the syntax.

The Do While loop will check the condition at the end instead of in the beginning.

This is actually pretty important. Here's the syntax anyway:

Do


Loop While <condition>

Example

Dim x As Integer

x = 10

Do

MessageBox.Show(x)

x+=1

Loop While x < 15

Do Until loop:

The Do While loop will continue if the condition are True and stop if the condition

are False. The Do Until loop does the opposite, it will continue if the condition are

False and stop if the condition are True. It will loop Until the condition are met.

The syntax of the Do Until loop and also an example of it:

Syntax Code:

Do


Loop Until <condition>

Example:

Code:

Dim X As Integer = 312

Do

X /= 10

MessageBox.show(x)

Loop Until X = 0

For Loops

The For loop will loop a certain amount of times and when it have looped so many times it will

stop. When declaring a For loop you give it a name just like you do when you declares a

variable.This is the syntax for declaring a For loop:

For <loop_name> As <type> = <start> To <end>

'code inside the loop

Next

Ex 01:

For i As Integer = 0 To 2

MessageBox.Show(i)

Next

Ex 02:

For i As Integer = 1 To 10 Step 3

MessageBox.Show(i)

Next

CBool - use this function to convert to Bool data type

CChar - use this function to convert to Char data type

CDate - use this function to convert to Date type

CDbl - use this function to convert to Double data type

CDec - use this function to convert to Decimal data type

CInt - use this function to convert to Integer data type

CLng - use this function to convert to Long data type

CShort - use this function to convert to Short data type

CStr - use this function to convert to String data type

Built-in Converting Function

MsgBox ( ) Function

A function is similar to a normal procedure but the main purpose of the function is to accept a certain input from the user and return a value which is passed on to the main program to finish the execution. There are two types of functions, the built-in functions.

MsgBox ( ) Function

The objective of MsgBox is to produce a pop-up message box and prompt the user to click on a command button before he /she can continues. This format is as follows:

MsgBox(Prompt, Style Value, Title)

The first argument, Prompt, will display the message in the message box. The Style Value will determine what type of command buttons appear on the message box,. The Title argument will display the title of the message board.

The InputBox( ) Function

An InputBox( ) function will display a message box where the user can enter a value or a message in

the form of text. The format is

InputBox(Prompt, Title, default_text, x-position, y-position)

Prompt - The message displayed normally as a question asked.

Title - The title of the Input Box.

default-text - The default text that appears in the input field where users

can use it as his intended input or he may change to the message he wish to

key in.

x-position and y-position - the position or the coordinate of the input box.

Form Controls

A control is an object that can be drawn on to the Form to enable or enhance

user interaction with the application.

Examples of these controls, Textboxes, Buttons, Labels, Radio Buttons, etc.

All these Windows Controls are based on the Control class, the base class for

all controls. Visual Basic allows us to work with controls in two ways: at design

time and at runtime. Working with controls at design time means, controls are

visible to us and we can work with them by dragging and dropping them from

the Toolbox and setting their properties in the properties window. Working at

runtime means, controls are not visible while designing, are created

and assigned properties in code and are visible only when the application

is executed.

Button Event

The default event of the Button is the Click event. When a Button is clicked it responds with

the Click Event. The Click event of Button looks like this in code:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_

System.EventArgs) Handles Button1.Click

'You place the code here to perform action when Button is clicked

End Sub

TextBox Control

This control looks like a box and accepts input from the user. The TextBox is based on the

TextBoxBase class which is based on the Control class. TextBoxes are used to accept input

from the user or used to display text. By default we can enter up to 2048 characters in a

TextBox but if the Multiline property is set to True we can enter up to 32KB of text. The image

below displays a Textbox.

TextBox Event

Private Sub TextBox1_TextChanged(ByVal sender

As System.Object, ByVal e As _System.EventArgs)

Handles TextBox1.TextChanged

End Sub

RichTextBox

RichTextBoxes are similar to TextBoxes but they provide some advanced features over the

standard TextBox. RichTextBox allows formatting the text, say adding colors, displaying

particular font types and so on.

RichTextBox Event

Private Sub RichTextBox1_TextChanged(ByVal sender

As System.Object, _

ByVal e As System.EventArgs) Handles

RichTextBox1.TextChanged

End Sub

Private Sub Italic_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Italic.Click

RichTextBox1.SelectionStart = RichTextBox1.Find("are")

'using the Find method to find the text "are" and setting it's

'return property to SelectionStart which selects the text to format

Dim ifont As New Font(RichTextBox1.Font, FontStyle.Italic)

'creating a new font object to set the font style

RichTextBox1.SelectionFont = ifont

'assigning the value selected from the RichTextBox the font style

End Sub

Private Sub Font color_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

Fontcolor.Click

RichTextBox2.SelectionStart = RichTextBox2.Find("are")

'using the Find method to find the text "are" and setting it's return

'property to SelectionStart which selects the text

RichTextBox2.SelectionColor = Color.Blue

'setting the color for the selected text with SelectionColor property

End Sub

Private Sub save_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles save.Click

RichTextBox3.SaveFile("hello.rtf")

'using SaveFile method to save text in a rich text box to hard disk

End Sub

Private Sub load_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles load.Click

RichTextBox4.LoadFile("hello.rtf")

'using LoadFile method to read the saved file

End Sub

Label, LinkLabel

Label

Labels are those controls that are used to display text in other parts of the application. They

are based on the Control class.

Notable property of the label control is the text property which is used to set the text for the

label.

Working with Linked labels

Private Sub LinkLabel1_LinkClicked(ByVal sender As

System.Object, ByVal_

e As System.Windows.Forms.LinkLabelLinkClickedEventArgs)_

Handles LinkLabel1.LinkClicked

System.Diagnostics.Process.Start("www.google.com")

'using the start method of system.diagnostics.process class

'process class gives access to local and remote processes

End Sub

CheckBox

CheckBoxes are those controls which gives us an option to select, say, Yes/No or True/False.

A checkbox is clicked to select and clicked again to deselect some option. When a checkbox

is selected a check (a tick mark) appears indicating a selection.

CheckBox Event

Private Sub CheckBox1_CheckedChanged(ByVal

sender As System.Object, _


CheckBox1.CheckedChanged

End Sub

Code to check a CheckBox's state using a button Event



If CheckBox1.Checked = True Then

TextBox1.Text = "Checked"

Else

TextBox1.Text = "UnChecked"

End If

End Sub

RadioButton

RadioButtons are similar to CheckBoxes but RadioButtons are displayed as rounded instead

of boxed as with a checkbox. Like CheckBoxes, RadioButtons are used to select and

deselect options but they allow us to choose from mutually exclusive options.

RadioButton Event

Private Sub RadioButton1_CheckedChanged(ByVal

sender As System.Object,_


RadioButton1.CheckedChanged

End Sub

Code to check a RadioButton's state Using a Button Event



If RadioButton1.Checked = True Then

TextBox1.Text = "Selected"

Else

TextBox1.Text = "Not Selected"

End If

End Sub

ListBox

The ListBox control displays a list of items from which we can make a selection. We can

select one or more than one of the items from the list.

Button 1Button 2

Button 3TextBox 4

TextBox 1

TextBox 2

TextBox 3

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles Button1.Click

TextBox1.Text = ListBox1.SelectedIndex

TextBox2.Text = ListBox1.Items.Count

TextBox3.Text = ListBox1.SelectedItem

End Sub



ListBox1.Items.Clear()

End Sub



ListBox1.Items.RemoveAt(TextBox5.Text)

End Sub

ComboBox

ComboBox is a combination of a TextBox and a ListBox. The ComboBox displays an editing

field (TextBox) combined with a ListBox allowing us to select from the list or to enter new text.

ComboBox displays data in a drop-down style format.

TreeView

The tree view control is used to display a hierarchy of nodes (both parent, child). You can

expand and collpase these nodes by clicking them. This control is similar to Windows

Explorer which displays a tree view in it's left pane to list all the folders on the hard disk.

1

2

Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, ByVal e As

System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterSelect

Label1.Text = e.Node.FullPath

End Sub

CheckedListBox

As the name says, CheckedListBox is a combination of a ListBox and a CheckBox. It displays a

ListBox with a CheckBox towards it's left.

Panel

Panels are those controls which contain other controls, for example, a set of radio buttons,

checkboxes, etc. Panels are similar to Groupboxes but the difference, Panels cannot display

captions where as GroupBoxes can and Panels can have scrollbars where as GroupBoxes can't. If

the Panel's Enabled property is set to False then the controls which the Panel contains are also

disabled.

GroupBox Control

As said above, Groupboxes are used to Group controls. GroupBoxes display a frame around them

and also allows to display captions to them which is not possible with the Panel control.

PictureBox Control

PictureBoxes are used to display images on them. The images displayed can be anything varying

from Bitmap, JPEG, GIF, PNG or any other image format files.

ToolTip, ErrorProvider

ToolTip

ToolTips are those small windows which display some text when the mouse is over a control

giving a hint about what should be done with that control. ToolTip is not a control but a

component which means that when we drag a ToolTip from the toolbox onto a form it will be

displayed on the component tray.

Private Sub Form1_Load(ByVal sender As

System.Object, ByVal e_

As System.EventArgs) Handles MyBase.Load

ToolTip1.SetToolTip(TextBox1, "Do not leave this

blank")

End Sub

ErrorProvider Component

The ErrorProvider component provides an easy way to set validation errors. It allows us to set

an error message for any control on the form when the input is not valid. When an error

message is set, an icon indicating the error will appear next to the control and the error

message is displayed as Tool Tip when the mouse is over the control.

Private Sub Button1_Click(ByVal sender As

System.Object, ByVal e_

As System.EventArgs) Handles

Button1.Click

If TextBox1.Text = "" Then

ErrorProvider1.SetError(TextBox1, "Cannot

leave textbox blank")

Else

ErrorProvider1.SetError(TextBox1, "")

End If

End Sub

Menus

Menus allow us to make a selection when we

want to perform some action with the application,

for example, to format the text, open a new file,

print and so on. In VB .NET Main Menu is the

container for the Menu structure of the form.

Menus are made of Menu Item objects that

represent individual parts of a menu (like File-

>New, Open, Save, Save As etc).

The two main classes involved in menu handling

are, Main Menu and Menu Item. The Main Menu

class let's us assign objects to a form's menu

class and Menu Item is the class which supports

the items in a menu system. Menus like File,

Edit, Format etc and the items in those Menus

are supported by this Menu Item class. It's this

Menu Item's click event that makes these Menus

work. For a Menu Item to be displayed, we need

to add it to a Main Menu object.

Date Time Picker

Date Time Picker allows us to select date and time. Date Time Picker is based on the control class.

When we click on the drop-down arrow on this control it displays a month calendar from which we

can make selections. When we make a selection that selection appears in the textbox part of the

Date Time Picker. The image below displays the Date Time Picker.

Private Sub DateTimePicker1_ValueChanged(ByVal

sender As System.Object, ByVal e As

System.EventArgs) Handles

DateTimePicker1.ValueChanged

TextBox1.Text = DateTimePicker1.Text

End Sub

Month Calendar

The Month Calendar control allows us to select date. The difference between a Date Time

Picker and Month Calendar is, in Month Calendar we select the date visually and in Date Time

Picker when we want to make a selection we click on the drop-down arrow and select the date

from the Month Calendar which is displayed. The image below displays a Month Calendar

control.

Private Sub MonthCalendar1_DateChanged(ByVal

sender As System.Object, ByVal e As

System.Windows.Forms.DateRangeEventArgs)

Handles MonthCalendar1.DateChanged

TextBox4.Text

=MonthCalendar1.SelectionStart.ToLongDateString

End Sub

Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs)

Handles Timer1.Tick

Label1.Text = TimeOfDay

End Sub

The Timer control allows you to set a time interval to execute an event after that interval

continuously. It is useful when you want to execute certain applications after a certain

interval.

The Timer

Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles

Timer1.Tick

Label1.Text = Format(Now, "dddd")

Label2.Text = Format(Now, "mm")

Label3.Text = Format(Now, "yyyy")

Label4.Text = System.DateTime.Now.ToString("dd-MMM-yyyy")

End Sub

Date Formatting

Creating a Simple Calculator

Creating User defined method to calculate totals

Private Sub CalculateTotals()

str2 = TextBox1.Text

Select Case calcFunc

Case "+"

str1 = str1 + str2

Case "-"

str1 = str1 - str2

Case "/"

str1 = str1 / str2

Case "*"

str1 = str1 * str2

End Select

TextBox1.Text = str1

inputStatus = True

End Sub

Declaring Variables

Dim str1 As Double

Dim str2 As Double

Dim calcFunc As String

Dim inputStatus As Boolean

Button Event



If inputStatus = False Then

TextBox1.Text += Button1.Text

Else

TextBox1.Text = Button1.Text

inputStatus = False

End If

End Sub

Operation Button Events

Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles btnAdd.Click

If TextBox1.Text.Length <> 0 Then

If calcFunc = "" Then

str1 = TextBox1.Text

TextBox1.Text = ""

Else

CalculateTotals()

End If

calcFunc = btnAdd.Text

End If

Clear Button Event

Private Sub Clear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles Clear.Click

TextBox1.Text = ""

str1 = 0

str2 = 0

calcFunc = "“

End Sub

Equal Button event

Private Sub Equal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles Equal.Click

If TextBox1.Text.Length <> 0 And str1 <> 0 Then

CalculateTotals()

calcFunc = "“

End If

End Sub

Database Access

What is a database?

A database is a collection of information that is organized so that it can easily be accessed,

managed, and updated. In one view,

Connection - Establishes a connection to a specific data source.

Data Provider?

A data provider in the .NET Framework serves as a bridge between an application and a

data source. A data provider is used to retrieve data from a data source and to resolve

changes to that data back to the data source.

Data Adapters?

Adapters are used to exchange data between a data source and a dataset.

A Dataset?

Represents a complete set of data including the tables that contain, order, and constrain the

data, as well as the relationships between the tables.

Introducing

ADO.NET

ADO.NET is the .NET platform’s new database technology, and it builds

on ADO (Active Data Objects).

ADO.NET provides DataSet and DataTable objects that are optimized for

moving disconnected sets of data across the Internet and intranets,

including through firewalls. At the same time, ADO.NET includes the

traditional connection and command objects, as well as an object called a

DataReader, (which resembles a forward-only, read-only ADO Record Set, in

case you’re familiar with ADO).

Together, these objects provide the best performance and throughput

for retrieving data from a database.

ADO.NET architecture

The ADO.NET Data Architecture

Data Access in ADO.NET relies on two components: DataSet and Data Provider.

DataSet

The dataset is a disconnected, in-memory representation of data. It can be considered as a

local copy of the relevant portions of the database. The DataSet is persisted in memory and

the data in it can be manipulated and updated independent of the database. When the use of

this DataSet is finished, changes can be made back to the central database for updating. The

data in DataSet can be loaded from any valid data source like Microsoft SQL server database,

an Oracle database or from a Microsoft Access database.

Data Provider

The Data Provider is responsible for providing and maintaining the connection to the database.

A DataProvider is a set of related components that work together to provide data in an efficient

and performance driven manner. The .NET Framework currently comes with two

DataProviders: the SQL Data Provider which is designed only to work with Microsoft's SQL

Server 7.0 or later and the OleDb DataProvider which allows us to connect to other types of

databases like Access and Oracle. Each DataProvider consists of the following component

classes:

The Connection object which provides a connection to the database

The Command object which is used to execute a command

The DataReader object which provides a forward-only, read only, connected recordset

The DataAdapter object which populates a disconnected DataSet with data and performs

update

Attaching the code

Connecting to a Database

To access data in a database, you must first establish a connection using an ADO.NET

connection object. Multiple connection objects are included in the .NET Framework, such

as the OleDbConnection object (for working with the same OLE DB data providers you

would access through traditional ADO) and the SqlConnection object (for optimized

access to Microsoft SQL Server).To create an object variable of type OleDbConnection

and initialize the variable to a new connection, you could use a statement like this

Dim <Connection Name> As New OleDb.OleDbConnection()

Possible Parameters for ConnectionString

Parameter Description

Provider The name of the data provider (Jet, SQL, and so on)

to use.

Data

Source

The name of the data source (database) to connect to.

User ID A valid username to use when connecting to the data

source.

Password A password to use when connecting to the data

source.

SERVER The network name of the data source server.

1. Specify the ConnectionString property of your ADO.NET connection now by placing

the following statement in the Load event of your form:

<Connection Name>.ConnectionString = _

“Provider=Microsoft.Jet.OLEDB.4.0; Data Source=<Database Source>”

2. After the connection string is defined, a connection to a data source is established by

using the Open () method of the connection object. Add the following statement to the

Load event, right after the statement that sets the connection string:

<Connection Name>.Open()

Closing a Connection to a Data Source

You should always explicitly close a connection to a data source. That means you

shouldn’t rely on a variable going out of scope to close a connection. Instead, you should

force an explicit disconnect via code. This is accomplished by calling the Close() method

of the connection object.

<Connection Name>.Close()

or

<Connection Name>.Dispose()

Manipulating Data

Understanding DataTables

DataTables contain a snapshot of data in the data source.

You generally start by filling a DataTable, manipulating its results, and finally sending

the changes back to the data source. The DataTable is populated using the Fill() method

of a DataAdapter object, and changes are sent back to the database using the Update()

method of a DataAdapter. Any changes made to the DataTable appear only in the local

copy of the data until you call the Update method. Having a local copy of the data

reduces contention by preventing users from blocking others from reading the data while

it’s being viewed.

If you’re familiar with ADO, you’ll note that this is similar to the Optimistic Batch Client

Cursor in ADO.

Creating a DataAdapter

To populate a DataTable, you must create a DataAdapter. The DataAdapter you’re

going to create will use the connection you’ve already defined to connect to the data

source and then execute a query you’ll provide.

The results of that query will be pushed into a DataTable. As mentioned earlier, there

are multiple connection objects in the .NET Framework.There are multiple ADO.NET

DataAdapter objects as well. You’ll be using the OleDbDataAdapter because you will

be connecting to Microsoft SQL Server.The constructor for a DataAdapter optionally

takes the command to execute when filling a DataTable or DataSet, as well as a

connection specifying the data source (you could have multiple connections open in a

single project).

This constructor has the following syntax:

Dim <Adapter Name> As New OleDb.OleDbDataAdapter ([CommandText],[Connection]);

To add a DataAdapter to your project, follow these steps:

1. Add the following statement immediately below the statement you entered to declare the <Connection

Name> object (in the class header, not in the Load event) to create a variable:

Dim <Data Adapter Name> As OleDb.OleDbDataAdapter

2. Add the following statement at the bottom of the Load event of the form (immediately following the

statement that opens the connection):

<Data Adapter Name> = New OleDb.OleDbDataAdapter(“Select * From <Table Name>”,<Connection Name>)

You must specify the insert, update, and delete statements to use to submit changes from the DataTable to

the data source. ADO.NET lets you customize how updates are submitted by enabling you to manually

specify these statements as database commands or stored procedures. In this case, you‟re going to have

ADO.NET automatically generate these statements for you by creating a CommandBuilder object.

3. Enter this statement in the class header to create the CommandBuilder variable:

Dim <Command Name> As OleDb.OleDbCommandBuilder

The CommandBuilder is an interesting object in that after you initialize it, you no longer work with it directly: It

works behind the scenes to handle the updating, inserting, and deleting of data. To make this work, you have

to attach the CommandBuilder to a DataAdapter. You do so by passing a DataAdapter to the

CommandBuilder. The CommandBuilder then registers for update events on the DataAdapter and provides

the insert, update, and delete commands as needed.

4. Add the following statement to the end of the Form_Load event to initialize the CommandBuilder object:

<Command Name> = New OleDb.OleDbCommandBuilder(<Data Adapter Name> )

Creating and Populating DataTables

1. Create the DataTable variable by adding the following statement on the class header to

create another variable:

Dim <Data set Name> As New DataTable

2. You’re going to use an integer variable to keep track of the user’s current position

(row) within the DataTable. To do this, add the following statement immediately below

the statement you just entered to declare the new DataTable object:

Dim < rowPosition variable Name > As Integer = 0

3. You now have a DataAdapter that allows access to a data source via the

connection.You’ve declared a DataTable that will hold a reference to data. Next add the

following statement to the Load event of the form, after the existing code, to fill the

DataTable with data:

<Data Adapter Name>.Fill(<Dataset Name>)

Search Records.

Dim <Input Variable Name> As String = <Input Filed Name>.Text

Try

If <Input Variable Name> <> "" Then

< Command Name >.CommandText = "SELECT <Filed1,Field2,….> FROM <Table Name>

WHERE <Primary Key Field>=" & CInt(<Input Filed Name>.Text )

< Command Name >. Connection = <Connection Name>

Dim <Data Reader Name> As OleDbDataReader = < Command Name >.ExecuteReader

If <Data Reader Name> .Read = True Then

<TextBox Name>.Text = <Data Reader Name> .Item(<Row Index >).ToString

<TextBox Name>.Text = <Data Reader Name> .Item(<Row Index >).ToString

…….

<Data Reader Name> . Close()

Exit Sub

Else

<Data Reader Name> .Close()

MsgBox("Record not Found: Want to add a Record?")

Exit Sub

End If

End If

Catch ex As Exception

End Try

Dim <Command Name> As New OleDbCommand

Add, Edit, Delete, Update

Records.

Creating New Records

Adding records to a DataTable is performed much like editing records. However, to create a

new row in the DataTable, you must first call the NewRow() method. After creating the new

row, you can set its column values. Follow these steps:

Dim <Datarow Variable Name> As DataRow = <Dataset name>.NewRow()

<Datarow Variable Name> (“<Field Name>”) = <textbox Name>.Text

<Datarow Variable Name> (“<Field Name>”) = <textbox Name>.Text

………

<Dataset name>.Rows.Add(<Datarow Variable Name>)

< Data Adapter Name >.Update(Dataset name)

<rowPosition variable Name>= <Dataset name>.Rows.Count - 1

Editing Records

To edit records in a DataTable, you change the value of a particular column in the desired

DataRow. Remember, though, that changes aren‟t made to the original data source until you

call Update () on the DataAdapter, passing in the DataTable containing the changes. You‟re

now going to add a button that the user can click to update the current record. Follow these

steps:

Double-click the Save button and add the following code to its Click event:

If <Dataset name>.Rows.Count <> 0 Then

<Dataset name>.Rows(<rowPosition variable Name>)(“<Field Name>”) = <textbox

Name>.Text

<Dataset name>.Rows(<rowPosition variable Name>)(“<Field Name>”) = <textbox

Name>.Text

…..


End If

Deleting Records

To delete a record from a DataTable, you call the Delete() method on the DataRow to be

deleted. Follow these steps:

1. Add a new button to your form (not to the group box) and set its properties as shown in

the following table:

2. Double-click the Delete button and add the following code to its Click event:

„ If there is data, delete the current row.

If <dataset Name>.Rows.Count <> 0 Then

<Dataset name>.Rows(<rowPosition variable Name>).Delete()


<rowPosition variable Name>= 0

End If

Data Validation

Private Sub TextBox1_LostFocus(ByVal sender As Object, ByVal e As

System.EventArgs) Handles TextBox1.LostFocus

If TextBox1.Text = "" Or IsNumeric(TextBox1.Text) Then

ErrorProvider1.SetError(TextBox1, "Cant leave blank or cant be

numeric value")

TextBox1.Focus()

End If

End Sub

To check weather the entered text is numeric or not we can use “is numeric”

method to ensure data and validate it.

Error Handling

Try … Catch

VB.NET has a inbuilt class that deals with errors. The Class is called Exception.

When an exception error is found, an Exception object is created. The coding

structure VB.NET uses to deal with such Exceptions is called the Try … Catch

structure.

In the coding area for your button, type the word Try. Then hit the return key on

your keyboard. VB.NET completes the rest of the structure for you:

Try


End Try

The Try word means "Try to execute this code". The Catch word means "Catch

any errors here". The ex is a variable, and the type of variable it is is an Exception

object.

Try

rt1.LoadFile("C:\test10.txt", RichTextBoxStreamType.PlainText)


End Try

When you run your programme, VB will Try to execute any code in the Try part. If everything

goes well, then it skips the Catch part. However, if an error occurs, VB.NET jumps straight to

Catch. Add the following to your Catch part:

MsgBox(ex.Message)

Because ex is an object variable, it now has its own Properties and methods. One of these is

the Message property. Run your programme and test it out. Click your button. You should see

the following error message:

The one we didn't handle. But the point about this new message box is that it will not crash

your programme. You have handled the Exception, and displayed an appropriate message for

the user.

If you know the kind of error that a programme might throw, you can get what Type it is from

the Error message box you saw earlier. This one:

Click the View Details links

under Actions to see the

following:

The first line tells us the Type of Exception it is:

System.IO.FileNotFoundException

You can add this directly to the catch part. Previously, you were just catching any error that

might be thrown:


But if you know a "file not found" error might be thrown, you can add that to the Catch line,

instead of Exception:

Catch ex As System.IO.FileNotFoundException

You can keep the Exception line as well. (You can have as many Catch parts as you want.)

This will Catch any other errors that may occur:

Try

rt1.LoadFile("C:\test10.txt", RichTextBoxStreamType.PlainText)

Catch ex As System.IO.FileNotFoundException

MsgBox(ex.Message)


MsgBox(ex.Message)

End Try

Try … Catch ….Finally:

Try


Finally

End Try

The Finally part is always executed, whether an error occurs or not. You typically add a Finally

part to perform any cleanup operations that are needed. For example, you may have opened

a file before going into a Try … Catch Statement. If an error occurs, the file will still be open.

Whether an error occurs or not, you still need to close the file. You can do that in the Finally

part.

Crystal Report

How to Creating a Report Using Crystal report in VB.NET?

Using Existing Dataset

1. Open the solution Explorer Window.

2. R.Click on the windows application name.

3. Select add >select “add new Item”.

4. Select Crystal Report from the template list.

5. Select “Add” button.

If the System Popup crystal registration wizard, close that window. Then you will see

crystal report gallery

1

2

3

4

56

7

8

9

10

1. Select “Using the Report Expert” option.Select “OK”.

2. Select “History” from the standard report creation wizard.

3. Click the Browse Button.

4. Select relevant dataset

5. select open button.

6. Select Finish button

7. Select the required table that you wish to add to

the report.

8.Select” Next”.

9.Select the required Fields that you wish to Display

on the report.

10.Select” Next” continuously until get finish button.

11.Select “Finish button”.

12.The Report Design Window Appears

13.At the left side of the report design view, you will

see “field Explorer” window.

14.If you wish, you can use properties window to

change properties of the report..

13

How to Creating a Report Using Crystal report in VB.NET?

Using Database file

1. Open the solution Explorer Window.

2. R.Click on the windows application name.

3. Select add >select “add new Item”.

4. Select Crystal Report from the template list.

5. Select “Add” button.

If the System Popup crystal registration wizard, close that window. Then you will see

crystal report gallery

1

2

3

5

6

4

7

8

9 10

1. Select “Using the Report Expert” option.Select “OK”.

2. Select “Database Files” from the standard report creation wizard.

3. Click the Browse button & Select relevant database

4. select open button.

5. Select the table that want to be insert

6. Click the add button to add the table

7.Select” Next”.

8.Select the required Fields that you wish to Display

on the report.

9.Select” Next” continuously until get finish button.

10.Select “Finish button”.

11.The Report Design Window Appears

12.At the left side of the report design view, you will

see “field Explorer” window.

13.If you wish, you can use properties window to

change properties of the report..

12

Viewing the Crystal Report

How to display the Report (How to view data)

1. Add new windows form in to the Application.

2. Select “Crystal report viewer” tool from the tool box.

3. Draw the suitable surface to display the content..

4. Select the properties window & select the “Report source” item & browse for

the created repot.

5. Select “open”.

6. Select “save”.

7. At the Form load event you will see the data in the Report..

Browse the report that

have been created

Date post:	25-Oct-2014
Category:	Documents
Upload:	khaled-salahul-den
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