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CS0004: Introduction to Programming Select Case Statements and Selection Input.

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1 CS0004: Introduction to Programming Select Case Statements and Selection Input

2 Review  A condition is either…  True or False  Relational Operators ==  <> << >>  <=  >=  Logical Operators  And  Or  Not

3 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 Select

4 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 5

5 Select Case Examples  New Topics:  Select Case Statements  Ranges

6 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.

7 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 = False

8 Select Case Statement with Radio Buttons Example  New Topics:  Radio Buttons  CheckChanged Event Procedure  Checked Property

9 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.

10 List Box Example  New Topics:  List Box  Design time list items

11 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 CheckChanged

12 Check Box Example  New Topics:  Check Boxes  Font Property  Font Class  New Keyword

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