Checkbox

The CheckBox control allows the user to turn an option on or off by ticking or clearing a box. In many applications, several checkboxes can be selected at once.

A common real-world example is the Font dialog box in word processors such as Microsoft Word, where the user may choose several effects such as underline, superscript, or small caps at the same time.

In Visual Basic 2015, checkboxes are also useful for shopping carts, option panels, questionnaires, settings pages, and formatting tools.

In this example, a simple shopping cart is created using six checkboxes, a label for the total amount, and two buttons. Each item has a fixed price declared by using the Const keyword.

If a checkbox is ticked, its Checked property is True. The program then adds the corresponding item price to the total by using the += operator. For example:

sum += BN

means the same as:

sum = sum + BN

Finally, the total is displayed in currency format by using ToString("c").

Public Class Form1

Private Sub BtnCal_Click(sender As Object, e As EventArgs) Handles BtnCal.Click
    Const LX As Integer = 100
    Const BN As Integer = 500
    Const SD As Integer = 200
    Const HD As Integer = 80
    Const HM As Integer = 300
    Const AM As Integer = 150
    Dim sum As Integer

    If CheckBox1.Checked = True Then
        sum += LX
    End If

    If CheckBox2.Checked = True Then
        sum += BN
    End If

    If CheckBox3.Checked = True Then
        sum += SD
    End If

    If CheckBox4.Checked = True Then
        sum += HD
    End If

    If CheckBox5.Checked = True Then
        sum += HM
    End If

    If CheckBox6.Checked = True Then
        sum += AM
    End If

    LblTotal.Text = sum.ToString("c")
End Sub

Private Sub BtnReset_Click(sender As Object, e As EventArgs) Handles BtnReset.Click
    CheckBox1.Checked = False
    CheckBox2.Checked = False
    CheckBox3.Checked = False
    CheckBox4.Checked = False
    CheckBox5.Checked = False
    CheckBox6.Checked = False
End Sub

End Class

The Reset button clears all selections by setting each checkbox to False.

The next example uses three checkboxes to select item sizes such as large, medium, and small. Each selected checkbox contributes its fixed value to the total.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

    Const large As Integer = 10.0
    Const medium As Integer = 8
    Const small As Integer = 5
    Dim sum As Integer

    If CheckBox1.Checked = True Then
        sum += large
    End If

    If CheckBox2.Checked = True Then
        sum += medium
    End If

    If CheckBox3.Checked = True Then
        sum += small
    End If

    Label5.Text = sum.ToString("c")

End Sub

This example shows that the same checkbox logic can be reused in smaller and simpler selection systems.

Checkboxes can also be used for text formatting. In this example, three checkboxes represent Bold, Italic, and Underline. Whenever the user checks or unchecks an option, the label’s font style changes accordingly.

This program uses the CheckedChanged event, which responds whenever the check state changes.

Public Class Form1

Private Sub ChkBold_CheckedChanged(sender As Object, e As EventArgs) Handles ChkBold.CheckedChanged
    If ChkBold.Checked Then
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style Or FontStyle.Bold)
    Else
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style And Not FontStyle.Bold)
    End If
End Sub

Private Sub ChkItalic_CheckedChanged(sender As Object, e As EventArgs) Handles ChkItalic.CheckedChanged
    If ChkItalic.Checked Then
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style Or FontStyle.Italic)
    Else
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style And Not FontStyle.Italic)
    End If
End Sub

Private Sub ChkUnder_CheckedChanged(sender As Object, e As EventArgs) Handles ChkUnder.CheckedChanged
    If ChkUnder.Checked Then
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style Or FontStyle.Underline)
    Else
        LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style And Not FontStyle.Underline)
    End If
End Sub

End Class

The statement below keeps the same font family and size, but adds italic formatting:

LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style Or FontStyle.Italic)

The next statement removes italic formatting while preserving the rest of the label’s original font settings:

LblDisplay.Font = New Font(LblDisplay.Font, LblDisplay.Font.Style And Not FontStyle.Italic)

The same logic is used for bold and underline.