This lesson takes you through the Select Case block, a very useful decision-making structure in Visual Basic.
The Select Case block provides an efficient way for decision making which is used to execute one block of statement(s) among a list of statement blocks according to the determined value of an expression. The expression is preceded by the “Select Case” phrase. The choices are made based on the value of this expression.
Syntax
Select Case expression
Case value0
statements
Case value1
statements
Case value2
statements
...........
...............
Case else
statements
End select
Example
Dim num As Integer
num = Val(Text1.Text)
Select Case num
Case 0
Print "You have entered zero"
Case 1
Print "You have entered one"
Case 2
Print "You have entered two"
Case Else
Print "The number you entered is greater than 2"
End Select
One block of statement(s) will be executed depending upon the value of num. If num=0 then, Case 0 will be evaluated and if num =1 then Case 1 will be evaluated.
See the other forms of Select Case Structure in the following programs.
Example
Dim score As Integer
score = Val(Text1.Text)
Select Case score
Case 900 To 1000
Print "First position"
Case 800 To 899
Print "Second position"
Case 700 To 799
Print "Third position"
Case Else
Print "No position, try again"
End Select
Example
Dim num As Integer
num = Val(Text1.Text)
Select Case num
Case Is > 0
Print "Positive number"
Case Is < 0
Print "Negative number"
Case 0
Print "Zero"
End Select
Example
Select Case value
Case 0, 1, 2, 3, 4, 5
Print "The values are 0,1,2,3,4,5"
Case Else
Print "Other values"
End Select
Use the attached sample programs to see basic examples of Select … Case in action.
One of the programs (Numbers) uses a function called Val(). We haven’t learned about that one yet, but it is coming in a future lesson. In a nutshell, it converts the numbers in a string variable to a numeric value.