The radio button is also a very useful control in Visual Basic
2008. However, it operates differently from the check boxes. While the
checkboxes work independently and allows the user to select one or more items
, radio buttons are mutually exclusive, which means the user can only choose one
item only out of a number of choices. Here is an example which allows the users
to select one color only.
Example 18.1
The Code:
Dim strColor As String
Private Sub RadioButton8_CheckedChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles RadioButton8.CheckedChanged
strColor = "Red"
End Sub
Private Sub RadioButton7_CheckedChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles RadioButton7.CheckedChanged
strColor = "Green"
End Sub
Private Sub RadioYellow_CheckedChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles RadioYellow.CheckedChanged
strColor = "Yellow"
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Label2.Text = strColor
End Sub
Although the user may only select one item at a time,
he may make more than one selection if those items belong to different
categories. For example, the user wish to choose T-shirt size and color, he
needs to select one color and one size, which means one selection in each
category. This is easily achieved in VB2008 by using the Groupbox control
under the containers categories. After inserting the Groupbox into the form, you
can proceed to insert the radio buttons into the Groupbox. Only the radio
buttons inside the Groupbox are mutually exclusive, they are not mutually
exclusive with the radio buttons outside the Groupbox. In Example 18.2, the
users can select one color and one size of the T-shirt.
Example 18.2
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Dim strColor
As String
Dim strSize As String
Private Sub RadioButton8_CheckedChanged(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles RadioButton8.CheckedChanged
strColor = "Red"
End Sub
Private Sub RadioButton7_CheckedChanged(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles RadioButton7.CheckedChanged
strColor = "Green"
End Sub
Private Sub RadioYellow_CheckedChanged(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles RadioYellow.CheckedChanged
strColor = "Yellow"
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Label2.Text = strColor
Label4.Text = strSize
End Sub
Private Sub RadioXL_CheckedChanged(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles RadioXL.CheckedChanged
strSize = "XL"
End Sub
Private Sub RadioL_CheckedChanged(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles RadioL.CheckedChanged
strSize = "L"
End Sub
Private Sub RadioM_CheckedChanged(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles RadioM.CheckedChanged
strSize = "M"
End Sub
Private Sub RadioS_CheckedChanged(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles RadioS.CheckedChanged
strSize = "S"
End Sub
