If and select statement

Conditional Statement
Prepared By :- Rahul Sharma
Enrollment No. : 07521102013
Subject :- VB .NET
Faculty :- Mr. Neeraj Mishra

Selection or Condition Construct
 The selection or decision construct means the
execution of statement(s) depending upon the
condition-test.
 If a condition evaluates to True, a course-of-action (a
set of statements) is followed otherwise another
course-of-action is followed.
 This construct is also called decision construct as it
helps in decision making.

Selection or Condition Constructs
 VB provides two types of selection construct :
1. If statement
2. Select Case statement
 The If Statement : If statement of VB comes in
various forms & are given below:
1) If..Then Statement
2) If..Then..Else Statement
3) If..Then..ElseIf Statement
4) Nested Ifs

If..Then Statement
 Definition : An If..Then statement tests a particular
condition; if the condition evaluates to true, a course-of-action
is followed otherwise it is ignored.
Syntax :
If (boolean expression) Then
statements
End If
Example :
If txtAge.Text>=18 Then
MsgBox(“You are eligible to vote”)
End if

If..Then..Else Statement
 If..Then..Else statement provides an alternate choice to the user
i.e. if the condition is true then a set of statements are executed
otherwise another set of statements are executed.
Syntax :
If (boolean Expression) Then
VB Statement(s)
Else
VB Statement(s)
End If
Example :
If (txtAge.Text>=18) Then
MsgBox(“You are eligible to vote”)
Else
MsgBox(“Sorry, You are not eligible to vote”)
End If

If..Then..ElseIf Statement
 If..Then..ElseIf statement is used to test a number of mutually
exclusive cases and only executes one set of statements for the case
that is true first.
Example:
If (Age<=4) Then
MsgBox(“Your rate is free.”)
ElseIf (Age<=12) Then
MsgBox(“You qualify for the children’s
rate.”)
ElseIf (Age<65) Then
MsgBox(“You must pay full rate”)
Else
MsgBox(“You qualify for the seniors’
rate.”)
End If
Syntax :
If (Boolean Expression) Then
Statement(s)
ElseIf (Boolean Expression 2) Then
Statement(s)
ElseIf (Boolean Expression 3) Then
Statement(s)
:
Else
Statement(s)
End If

Nested Ifs
 A nested If is an if that has another If in its if ’s body or in its
else’s body.
 The nested if can have one of the following 3 forms :-
1. If (expression 1) Then
If (expression 2 ) Then
Statement 1
Else
Statement 2
End If
Else
body-of-else
End If
body-of-if
Else
:
If (expression 2) Then
Statement-1
Else
Statement-2
End If

:
Statement-1
Else
Statement-2
End If
Else
Statement-3
Else
Statement-4
:
End If
End If
Example of Nested If:
If Num>0 Then
Msgbox(“It is a positive number”)
Else
If Num<0 Then
Msgbox(“It is a negative number”)
Else
Msgbox(“The number is equal to
zero”)
End If
End If

Select-Case Statement
 Select-Case is a multiple branching statement and is
used to executed a set of statements depending upon
the value of the expression.
 It is better to use Select-Case statement in comparison
to If..Then..ElseIf Statement when the number of
checks are more.
 There are 3 different forms of using Select-Case
statements and are given below :

Different forms of Select-Case
1. Select Case : Simplest Form [Exact match]
Select Case Expression
Case Value
’visual basic statements
Case Value
Case Else
End Select
Example :
Select Case byMonth
Case 1,3,5,7,8,10,12
number_of_days=31
Case 2
number_of_days=28
Case Else
number_of_days=30
End Select

2.Select Case : Second Form [Relational Test]
Case Is relation
Case Is relation
Case Else
End Select
Example:
Select Case marks
Case Is < 50
Result = “Fail”
Case Is < 60
Result = “Grade B”
Case Is < 75
Result = “Grade A”
Case Else
Result = “Grade A+”
End Select

3.Select Case : Third Format [Range Check]
Case exp1 To exp2:
Case exp1 To exp2:
Case Else:
End Select
Example :
Select Case Age
Case 2 to 4 : Msgbox(“PreNursery”)
Case 4 to 6 : Msgbox(“Kindergarden”)
Case 6 to 10 : Msgbox(“Primary”)
Case Else : Msgbox(“Others”)
End Select

If and select statement

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