Page 166 - Open Soource Technologies 304.indd

Event Driven Programming

Private Sub btnNumber_Click(...) Handles btnNumber.Click
‘Determine the number of days in a season
Dim season As String
season = txtSeason.Text
txtNumDays.Text = season & “ has “ & NumDays(season) & “ days.”
End Sub
Function NumDays(ByVal season As String) As Integer
‘Look up the number of days in a given season
Select case season.ToUpper
Case “WINTER”
Return 87
Case “SPRING”
Return 92
Case “SUMMER”, “AUTUMN”, “FALL”
Return 93
End Select
End Function
[Run, type “Summer” into the text box, and press the button.]

Comments

1. In a Case clause of the form Case b To c, the value of b should be less than or equal
to the value of c. Otherwise, the clause is meaningless.
2. If the word Is, which should precede an inequality sign in a value list, is accidentally
omitted, the editor will automatically insert it when checking the line.
3. The items in the value list must evaluate to a literal of the same type as the selector. For
instance, if the selector evaluated to a string value, as in
4. Dim firstName As String
5. firstName = txtBox.Text

6. Select Case firstName
then the clause Case firstName.Length would be meaningless.

160 LOVELY PROFESSIONAL UNIVERSITY