Conditional Statements & Loops

Conditional Statements & Loops
21BCA2T332:Visual Programming
SIMMI S
Assistant Professor
Department Of Computer Science(UG)
Kristu Jayanti College, Autonomous

Statements in Visual Basic
A statement in Visual Basic is a complete instruction. It can contain
keywords, operators, variables, constants, and expressions.
Each statement belongs to one of the following categories:
• Declaration Statements
• Executable Statements
• Assignment Statements:
Simmi S,Department of Computer Science

Declaration statements
We use declaration statements to name and define procedures,
variables, properties, arrays, and constants.
Dim number As Integer

Executable statements
An executable statement performs an action. It can call a procedure,
branch to another place in the code, loop through several statements,
or evaluate an expression.
If (a < 50)
Then
' if condition is true then print the following ‘
Console.WriteLine("a is less than 20")
End If

Assignment statements
• Assignment statements carry out assignment operations, which
consist of taking the value on the right side of the assignment
operator (=) and storing it in the element on the left
Dim number As Integer
number=100

VISUAL BASIC CONDITIONAL STATEMENTS
 Conditional statements(Control Statements) in Visual Basic can be
used to take decisions based on certain conditions in your program.
We can define more than one condition to be evaluated by the
program with statements.
If the defined condition is true, the statement or block executes
according to the condition, and if the condition is false, another
statement is executed.

Conditional Statements
VB.NET provides the following conditional or decision-making
statements.
• If-Then Statement
• If-Then Else Statement
• If-Then ElseIf Statement
• Select Case Statement
• Nested Select Case Statements

If-Then Statement
• The If-Then Statement is a control statement that defines one or
more conditions, and if the particular condition is satisfied, it
executes a piece of information or statements.
If condition Then
[Statement or block of Statement]
End If

If-Then-Else Statement
The If-Then Statement can execute single or multiple statements. when the
condition is true, but when the expression evaluates to false, it does nothing.
The IF-Then-Else Statement is telling what If condition to do when if the
statement is false, it executes the Else statement.
Syntax:
If (Boolean_expression) Then
'This statement will execute if the Boolean condition is true
Else
'Optional statement will execute if the Boolean condition is false
End If

If-Then-ElseIf statement
The If-Then-ElseIf Statement provides a choice to execute only one
condition or statement from multiple statements.
Execution starts from the top to bottom, and it checked for each If
condition.
 And if the condition is met, the block of If the statement is executed.
And if none of the conditions are true, the last block is executed

Syntax:
If (condition 1) Then
' Executes when condition 1 is true
ElseIf ( condition 2) Then
' Executes when condition 2 is true
ElseIf ( boolean_expression 3) Then
' Executes when the condition 3 is true
Else
' executes the default statement when none of the above conditions is true
End If

If-Then Statement
Example:
Dim attendance As Integer
If attendance= 100 Then
Console.WriteLine(“100 % Attendance secured")
End If

If-Then-Else Statement
Example
Dim a As integer=10
Dim b As Integer=20
If a > b Then
Console.WriteLine(" A is greater”)
Else
Console.WriteLine(" B is greater”)
End If

Example:
If mark = 90 Then
Console.WriteLine(" Mark is 90")
ElseIf mark < 50 Then
Console.WriteLine(" Below 50% only")
ElseIf mark<30 Then
Console.WriteLine(" Just Pass")
Else
'if none of the above condition is satisfied, print the following statement
Console.WriteLine(" Failed")
End If Simmi S,Department of Computer Science

Select Case Statement
the Select Case statement is a collection of multiple case statements,
which allows executing a single case statement from the list of
statements.
 A selected case statement uses a variable to test for equality against
multiple cases or statements in a program.
If the variable is matched with any test cases, that statement will be
executed.
 And if the condition is not matched with any cases, it executes the
default statement.

Syntax:
Select Case [variable or expression]
Case value1 'defines the item or value that you want to match.
//define a statement to execute
Case value2 'defines the item or value that you want to match.
// Define a statement to execute
Case Else
// Define the default statement if none of the conditions is true.
End Select

Dim Days As String
Days = "Thurs"
Select Case Days
Case "Mon"
Console.WriteLine(" Today is Monday")
Case "Tue"
Console.WriteLine(" Today is Tuesday")
Case "Wed"
Console.WriteLine("Today is Wednesday")
Case "Thurs"
Console.WriteLine("Today is Thursday")
Case "Fri"
Console.WriteLine("Today is Friday")
Case "Sat"
Console.WriteLine("Today is Saturday")
Case "Sun"
Console.WriteLine("Today is Sunday")
Case Else
Console.WriteLine(" You have typed Something wrong")
End Select

VB.NET Loop
• A Loop is used to repeat the same process multiple times until it
meets the specified condition in a program. By using a loop in a
program, a programmer can repeat any number of statements up to
the desired number of repetitions.
Advantages of VB.NET loop
• It provides code iteration functionality in a program.
• It executes the statement until the specified condition is true.
• It helps in reducing the size of the code.
• It reduces compile time.

Types of Loops
There are five types of loops available in VB.NET:
• Do While Loop
• For Next Loop
• For Each Loop
• While End Loop
• With End Loop

Do Loop
In VB.NET, Do While loop is used to execute blocks of statements in the
program, as long as the condition remains true
Do [ { While | Until } condition ]
[ statements ]
Loop
' -or-
Do
[ statements ]
Loop [ { While | Until } condition ]

Do
[ Statements to be executed]
Loop While Boolean_expression
or
Do
[Statement to be executed]
Loop Until Boolean_expression

Dim i As Integer
Do While i < 5
Console.WriteLine(“Values: {0}", i)
i = i + 1
Loop
----------------------------------------------------------------------------------------------------------
Output
• values: 1
• values: 2
• values: 3
• values: 4

Dim k As Integer
k = 0
Do
Console.WriteLine("Number : {0}", k)
k = k + 1
Loop While k < 5
--------------------------------------------------------------------------------------------------------
Output
Number : 0
Number : 1
Number : 2
Number : 3
Number : 4

For Next Loop
• A For Next loop is used to repeatedly execute a sequence of code or a
block of code until a given condition is satisfied. A For loop is useful in
such a case when we know how many times a block of code has to be
executed.
• Syntax
For variable_name As [ DataType ] = start To end [ Step step ]
[ Statements to be executed ]
Next

For Next Loop
• For: It is the keyword that is present at the beginning of the definition.
• variable_name: It is a variable name, which is required in the For loop
Statement..
• [Data Type]: It represents the Data Type of the variable_name.
• start To end: The start and end are the two important parameters
representing the initial and final values of the variable_name..
• Step: A step parameter is used to determine by which the counter value of a
variable is increased or decreased after each iteration in a program. If the
counter value is not specified; It uses 1 as the default value.
• Statements: A statement can be a single statement or group of statements
that execute during the completion of each iteration in a loop.
• Next: In VB.NET a Next is a keyword that represents the end of the For loop's

For l As Integer = 1 To 10 Step 2
Console.WriteLine(" Value of variable i is : {0}", l)
Next
-------------------------------------------------------------------------------------------------------
Output
Value of variable i is : 1

For Each Loop
In the VB.NET, For Each loop is used to iterate block of statements in an array
or collection objects. Using For Each loop, we can easily work with collection
objects such as lists, arrays, etc., to execute each element of an array or in a
collection.
For Each var_name As [ DataType ] In Collection_Object
[ Statements to be executed]
Next

Dim f As String
Dim names() As String = {"apple", "orange", "kiwi"}
For Each f In names
Console.WriteLine(" items in array {0}", f)
Next
----------------------------------------------------------------------------------------------------------
Output
• items in array apple
• items in array orange
• items in array kiwi

For Each a In An_array
Console.WriteLine(" Value of a is {0}", a)
Next
--------------------------------------------------------------------------------------------
Output
• Value of a is 1
• Value of a is 2
• Value of a is 3
• Value of a is 4
• Value of a is 5

THANK YOU

Conditional Statements & Loops

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