CheckedListBox with RadioButton-style Behaviour

[jmcilhinney]

C# version here.

Imports System.ComponentModel
 
''' <summary>
''' Provides RadioButton-style functionality in a CheckedListBox.
''' </summary>
<ToolboxBitmap(GetType(CheckedListBox))> _
Public Class RadioCheckedListBox
    Inherits CheckedListBox
 
    ''' <summary>
    ''' Indicates whether the check boxes behave like radio buttons.
    ''' </summary>
    Private _radioCheck As Boolean = True
 
 
    ''' <summary>
    ''' Gets or sets a value that indicates whether the check boxes behave like radio buttons.
    ''' </summary>
    ''' <value>
    ''' <b>true</b> if only one item can be checked at a time; otherwise, <b>false</b>.
    ''' </value>
    <Category("Behavior")> _
    <Description("Indicates whether only a single item can be checked or not.")> _
    <DefaultValue(True)> _
    Public Property RadioCheck() As Boolean
        Get
            Return Me._radioCheck
        End Get
        Set(ByVal value As Boolean)
            If Me._radioCheck <> value Then
                Me._radioCheck = value
                Me.OnRadioCheckChanged(EventArgs.Empty)
            End If
        End Set
    End Property
 
 
    ''' <summary>
    ''' Raised when the <see cref="RadioCheck" /> property value changes.
    ''' </summary>
    ''' <remarks></remarks>
    Public Event RadioCheckChanged As EventHandler
 
 
    ''' <summary>
    ''' Raises the <see cref="RadioCheckChanged" /> event.
    ''' </summary>
    ''' <param name="e">
    ''' The data for the event.
    ''' </param>
    Protected Overridable Sub OnRadioCheckChanged(ByVal e As EventArgs)
        RaiseEvent RadioCheckChanged(Me, e)
    End Sub
 
    ''' <summary>
    ''' Raises the <see cref="ItemCheck" /> event.
    ''' </summary>
    ''' <param name="e">
    ''' The data for the event.
    ''' </param>
    ''' <remarks>
    ''' If an item is being checked, all other items are unchecked.
    ''' </remarks>
    Protected Overrides Sub OnItemCheck(ByVal e As System.Windows.Forms.ItemCheckEventArgs)
        If Me._radioCheck AndAlso e.NewValue = CheckState.Checked Then
            'An item is being checked so uncheck all others.
            For index As Integer = 0 To Me.Items.Count - 1
                If index <> e.Index Then
                    Me.SetItemChecked(index, False)
                End If
            Next
        End If
 
        MyBase.OnItemCheck(e)
    End Sub
 
End Class

[NickThissen]

Cool.

You could also add this code to let the control draw radiobuttons instead of checkboxes:

Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)
        MyBase.OnDrawItem(e)
 
        If e.Index >= 0 AndAlso e.Index < Me.Items.Count Then
 
            Dim checkRect As New Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Height, e.Bounds.Height)
            Dim state As ButtonState
            If Me.GetItemChecked(e.Index) Then
                state = ButtonState.Checked
            Else
                state = ButtonState.Normal
            End If
 
            ' Hide checkboxes
            Using b As New SolidBrush(Me.BackColor)
                e.Graphics.FillRectangle(b, checkRect)
            End Using
 
            ' Paint radio buttons
            ControlPaint.DrawRadioButton(e.Graphics, checkRect, state)
 
        End If
    End Sub

Unfortunately, they don't look like the actual OS radio buttons (they're close, but not exactly), but I'm not sure how else to draw a radio button without actually putting a radiobutton there... It does the job though

[jmcilhinney]

Nice idea Nick. The RadioButtonRenderer class might let you draw a themed radio button.

[NickThissen]

Nice idea Nick. The RadioButtonRenderer class might let you draw a themed radio button.

Ah, didn't know that. That looks much better

''' <summary>
    ''' Paints a RadioButton instead of a CheckBox on each item.
    ''' </summary>
    ''' <param name="e">The data for the event.</param>
    Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)
        MyBase.OnDrawItem(e)
 
        If Me.RadioCheck AndAlso e.Index >= 0 AndAlso e.Index < Me.Items.Count Then
 
            Dim checkRect As Rectangle = Me.GetCheckboxRectangle(e.Bounds)
 
            Dim state As VisualStyles.RadioButtonState
            If Me.GetItemChecked(e.Index) Then
                state = VisualStyles.RadioButtonState.CheckedNormal
            Else
                state = VisualStyles.RadioButtonState.UncheckedNormal
            End If
 
            ' Hide original checkbox
            Using b As New SolidBrush(Me.BackColor)
                e.Graphics.FillRectangle(b, checkRect)
            End Using
 
            ' Paint radio button
            RadioButtonRenderer.DrawRadioButton(e.Graphics, checkRect.Location, state)
 
        End If
    End Sub

I tried to implement hot-tracking (and different style when pressed), but it resulted in loads of flickering that I couldn't solve without having to draw the entire item manually. While that's not a lot of work I decided to let it go for now, it looks great already.


EDIT
I added a check for RadioCheck, so that it still draws normal checkboxes when it is false.

[JuggaloBrotha]

Someone wanna post the entire class' code?

[NickThissen]

Someone wanna post the entire class' code?

It's already in the first post..? Just paste my code snippet in if you need that too. Quote my post in order to copy the code without linenumbers.