CheckBox in Visual Basic .NET

Tags: VB.NET, VB 2008, VB 2010, VB 2012, VB 2013

This lesson describes the CheckBox control

CheckBox

Basically it's a box that the user can check and clear.

The CheckBox control provides a lots of events but the most used is certainly CheckChanged event that you could use to perform some action.

Same like a Button a CheckBox can display a textual caption, a picture, or both but unlike a RadioButton, each CheckBox choice is independent of all others CheckBox controls (if any).

design view

Usually we use the CheckBox control's Checked property to tell if it is checked (returns True if the CheckBox is checked and False if it is not).

Ok let's see an example of CheckBox. For instance, let's upgrade our previous example making the exit application optional, but before that change it's Name peroperty to ExitOption, change Text to "Is Exit Allowed?" and then double click the control to generate the CheckedChanged event handler.

properties

    Private Sub ExitOption_CheckedChanged(sender As Object, e As EventArgs) _
     Handles ExitOption.CheckedChanged
        
    End Sub
We gonna use a CheckedChanged event, that fires whenever the control's value changes so based on this value we allow and disallow exiting the application as shown in the following code:

    Private IsExitAllowed As Boolean ' a flag variable
    Private Sub ExitOption_CheckedChanged(sender As Object, e As EventArgs)_
     Handles ExitOption.CheckedChanged
        If ExitOption.Checked = True Then
            IsExitAllowed = True ' you can close the app
        Else
            IsExitAllowed = False ' you cannot close the app
        End If
    End Sub
Then use the flag variable in the Button's click event to make the exit optional:

    Private Sub ButtonExit_Click(sender As Object, e As EventArgs) _
     Handles ButtonExit.Click
        If IsExitAllowed = True Then
            Application.Exit()
        Else
            MessageBox.Show("You are not allowed to exit the application.")
        End If
    End Sub


Note: If your form requires say five or more CheckBox controls with related purposes, you may want to consider using a CheckedListBox instead.

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