Make DropDown CheckedListBox in VB.net

Updated 8/29/2018 - Formatted

 

In my recent window application there is need to create a Checked listbox that has dropdown functionality, so I created a user control with the help of checkedlistbox, textbox, button controls and windows.form object that is so useful for me.

 

This user controls have these features:

1. Control has drop down functionality
2. Control show status of selected items like 'All selected', 'None selected' and 'N items selected '.
3. We able to set the length of dropdown list.
4. We can bind items on design time or runtime etc.

 

 

How to make

 

Add a user control in your application with the name 'DropDownCheckedListBox'.

 

Add textbox, button, checkedlistbox controls in this user control set the position like below

 

 

 

Open code file and make some private variable and some public properties

Private Const T_DisplayListSize As Integer = 6
Private Const SelectNoneText As String = "(None Selected)"
Private Const SelectAllText As String = "(All Selected)"
Private Const SelectSomeText As String = "(Some Selected...)"
Private Frm As Form
Private LostFocus As Boolean
Private CodeValue As String
Private T_MustFill As Boolean
Private Shared m_ChkItemsString As String
Public Event DropDown()
Public Shadows Event TextChanged()
Public Event SetStatusPrompt(ByVal Sender As DropDownCheckedListBox)
Public Event AllItemSelected(ByVal Sender As DropDownCheckedListBox)
Public Event AllItemDeselected(ByVal Sender As DropDownCheckedListBox)

Public properties

 

Make some public properties for the itemslist and length of dropdown list etc. 

Private dataList() As String
Public Property Items() As String()
    Get
        Return dataList
    End Get
    Set(ByVal value As String())
        dataList = value
    End Set
End Property
Private ListSize As Integer
Public Property DisplayListSize() As Integer
    Get
        Return ListSize
    End Get
    Set(ByVal value As Integer)
        ListSize = value
        SetList()
    End Set
End Property
Private T_DroppedDown As Boolean
Public ReadOnly Property DroppedDown() As Boolean
    Get
        Return T_DroppedDown
    End Get
End Property
Private T_ListText As String
Public ReadOnly Property ListText() As String
    Get
        Return T_ListText
    End Get
End Property

Add new function InitializeNew() in Sub new()

Public Sub New()
    InitializeComponent()
    InitializeNew()
End Sub
Private Sub InitializeNew()
    Dim strTemp As String
    ListSize = T_DisplayListSize
    T_DroppedDown = False
    T_ListText = ""
    T_MustFill = False
    txt.Text = strTemp
    chkListBox.Hide()
    Frm = New Form
    With Frm
        .ShowInTaskbar = False
        .FormBorderStyle = FormBorderStyle.None
        .ControlBox = False
        .StartPosition = FormStartPosition.Manual
        .TopMost = True
        .Location = chkListBox.Location
        .Width = chkListBox.Width
        .Controls.Add(chkListBox)
    End With

    SetSize()

End Sub

Create mousedown event of btnDropDown button and call function listButtonClick on here. This is responsible for showing checkedListBox

Private Sub btnDropdown_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles btnDropdown.MouseDown
        ListButtonClick()
End Sub

We have already make two custom event one is TextChanged and another is DropDown, on here both event have been raised. So we can handle events when control changes its status(user check or uncheck item(s)).

Private Sub ListButtonClick()
    Dim strTemp As String
    strTemp = T_ListText
    If T_DroppedDown Then
        T_DroppedDown = False
        txt.Text = GetSelectedItems()
        chkListBox.Hide()
        Frm.Hide()
        txt.Focus()
        If Not strTemp = T_ListText Then
            RaiseEvent TextChanged()
        End If
    ElseIf Not LostFocus Then
        T_DroppedDown = True
        SetSize()
        Frm.Show()
        chkListBox.Show()
        chkListBox.Focus()
        RaiseEvent DropDown()
    End If
    LostFocus = False
End Sub

Private Sub SetList()
    Dim oFrm As Form
    Dim oRect As Rectangle
    Dim oPt As Point
    If Frm IsNot Nothing Then
        Frm.Height = (ListSize * chkListBox.ItemHeight) + 3
        chkListBox.Height = Frm.Height
        chkListBox.Top = 0
        oFrm = Me.FindForm
        If oFrm IsNot Nothing Then
            oPt = Me.ParentForm.PointToClient(Me.PointToScreen(Point.Empty))
            oPt.Y = oPt.Y + Me.txt.Height
            oRect = oFrm.RectangleToScreen(oFrm.ClientRectangle)
            oPt.X = oPt.X + oRect.Left
            oPt.Y = oPt.Y + oRect.Top
            Frm.Location = oPt
        End If
        Frm.Width = chkListBox.Width
    End If
End Sub

SetSize() function works for set the size of all controls if you can resize usercontrol.

Private Sub SetSize()
    LostFocus = False
    txt.Width = Me.Width
    btnDropdown.Left = txt.Width - btnDropdown.Width - 2
    chkListBox.Width = Me.Width
    Me.Height = txt.Height
    SetList()
 End Sub

Working with control

 

Build your application, the DropDownCheckedListBox should appear in your Visual Studio ToolBox and then you can drag and drop it on to your windows Form.

 

Add items on design time.

 

Click on items property, add strings and click ok

 

You can apply more functionalities according your need in this user control. You can download full source code sample.