Select Case Statements and Selection Input Review A condition is either True or False Relational Operators ltgt lt gt lt gt Logical Operators And Or Not Select Case Statements ID: 237504
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Slide1
CS0004: Introduction to Programming
Select Case Statements and Selection InputSlide2
Review
A condition is either…
True
or
False
Relational Operators
=
<>
<
>
<=
>=
Logical Operators
And
Or
NotSlide3
Select Case Statements
Sometimes you want to check if a variable is one of many values. You can do this with If statements:
Dim a As Integer
If a = 1 Then
‘do something
ElseIf
a = 2 Then
‘do something
ElseIf
a =
3 Then
‘do something
Else
‘do something
However, you can use
select case statements
, instead to form a more logical decision structure
Dim a As Integer
Select Case a
Case 1
‘
do
something
Case 2
‘do something
Case 3
‘do something
Case Else
‘do something
End SelectSlide4
Select Case Statements
General Form
Select Case
selector
Case
valueList1
action1
Case
valueList2
action2
Case
Else
actionOfLastResort
End Select
The value lists can be literals, variables, expressions, or a range in the form
a To b
where
a
and
b
are literals, variables, or expressions.
Value lists can also be multiple values separated by a comma, for instance you can have:
Case 1, 2, 5
This case will be executed if the
selector
is either 1, 2 or 5Slide5
Select Case Examples
New Topics:
Select Case Statements
RangesSlide6
Selection Input
Some controls in VB ask the user to make selections from multiple choices. Some Examples are:
Radio Buttons
Check Boxes
List Boxes
Radio buttons and check boxes can be grouped together using
group boxes
.
If controls are inside of a group box, it is said that the controls are
attached
to the group box.
If multiple radio buttons are in the same group box, only one of them can be selected at a time.Slide7
Radio Buttons
Radio buttons
are controls that when grouped, only one can be checked (selected) at a time.
Radio buttons default event procedure is
CheckedChanged
This event happens when a radio button is either first checked or unchecked.
Radio buttons have a property called
Checked
that holds the
boolean
value of whether the box is checked or not.
radButton.Checked
You can set whether a radio button is checked or not checked with this property
radButton.Checked
= True
radButton.Checked
= FalseSlide8
Select Case Statement with Radio Buttons Example
New Topics:
Radio Buttons
CheckChanged
Event Procedure
Checked PropertySlide9
List Boxes
An
input box
is a list of strings in which each can be selected.
We have added items to the list and cleared the list in previous examples
lstTheList.Items.Add
(parameter)
lstTheList.Items.Clear
()
You can also add items to the list box at design time in Visual Studio.
Click the task
button (the triangle) on the control in Visual Studio
.
Click on “Edit Items” on the menu that appears
Add each item in a single line in the dialog box.
Click “OK”
You can access the item currently selected by using the
Text
property of the list box.
The list box default event procedure is
SelectedIndexChanged
. This means that the item that is selected has changed.Slide10
List Box Example
New Topics:
List Box
Design time list itemsSlide11
Check Boxes
Check boxes
are like radio buttons, but multiple check boxes can be checked at once.
They also have a checked property
chkTheCheckBox.Checked
The default event procedure for a check box is
CheckChangedSlide12
Check Box Example
New Topics:
Check Boxes
Font Property
Font Class
New Keyword