VirtualCombo Control

Provides a virtual data combo box using the LBS_NODATA style for large dataset display, supplying data on demand, with support for owner-draw, incremental search, and OLE drag-drop.

Enumerations

VcbStyleConstants

Combo box style constants.

Constant	Value	Description
VcbStyleDropDownCombo	0	Drop-down combo box (editable)
VcbStyleSimpleCombo	1	Simple combo box
VcbStyleDropDownList	2	Drop-down list box (not editable)

VcbDrawModeConstants

Draw mode constants.

Constant	Value	Description
VcbDrawModeNormal	0	Standard draw mode
VcbDrawModeOwnerDrawFixed	1	Owner-draw fixed height mode

Properties

Name

Public Property Get Name() As String

Returns the name used to identify the object in code.

Tag

Public Property Get Tag() As String
Public Property Let Tag(ByVal Value As String)

Stores extra data needed by the program.

Parent

Public Property Get Parent() As Object

Returns the object containing the object.

Container

Public Property Get Container() As Object
Public Property Set Container(ByVal Value As Object)

Returns/sets the container of the object.

Left

Public Property Get Left() As Single
Public Property Let Left(ByVal Value As Single)

Returns/sets the distance between the left edge of the object and its container.

Top

Public Property Get Top() As Single
Public Property Let Top(ByVal Value As Single)

Returns/sets the distance between the top edge of the object and its container.

Width

Public Property Get Width() As Single
Public Property Let Width(ByVal Value As Single)

Returns/sets the width of the object.

Height

Public Property Get Height() As Single
Public Property Let Height(ByVal Value As Single)

Returns/sets the height of the object.

Visible

Public Property Get Visible() As Boolean
Public Property Let Visible(ByVal Value As Boolean)

Returns/sets whether the object is visible.

ToolTipText

Public Property Get ToolTipText() As String
Public Property Let ToolTipText(ByVal Value As String)

Returns/sets the tooltip text displayed when the mouse hovers.

HelpContextID

Public Property Get HelpContextID() As Long
Public Property Let HelpContextID(ByVal Value As Long)

Returns/sets the help context ID.

WhatsThisHelpID

Public Property Get WhatsThisHelpID() As Long
Public Property Let WhatsThisHelpID(ByVal Value As Long)

Returns/sets the associated context help ID.

DragIcon

Public Property Get DragIcon() As IPictureDisp
Public Property Let DragIcon(ByVal Value As IPictureDisp)
Public Property Set DragIcon(ByVal Value As IPictureDisp)

Returns/sets the icon displayed during drag-drop operations.

DragMode

Public Property Get DragMode() As Integer
Public Property Let DragMode(ByVal Value As Integer)

Returns/sets the drag mode.

hWnd

Public Property Get hWnd() As LongPtr

Returns the control handle.

hWndUserControl

Public Property Get hWndUserControl() As LongPtr

Returns the UserControl handle.

hWndEdit

Public Property Get hWndEdit() As LongPtr

Returns the edit box handle.

hWndList

Public Property Get hWndList() As LongPtr

Returns the drop-down list box handle.

Font

Public Property Get Font() As StdFont
Public Property Let Font(ByVal NewFont As StdFont)
Public Property Set Font(ByVal NewFont As StdFont)

Returns/sets the font.

VisualStyles

Public Property Get VisualStyles() As Boolean
Public Property Let VisualStyles(ByVal Value As Boolean)

Returns/sets whether visual styles are enabled. Requires comctl32.dll 6.0 or later.

BackColor

Public Property Get BackColor() As OLE_COLOR
Public Property Let BackColor(ByVal Value As OLE_COLOR)

Returns/sets the background color.

ForeColor

Public Property Get ForeColor() As OLE_COLOR
Public Property Let ForeColor(ByVal Value As OLE_COLOR)

Returns/sets the foreground color.

Enabled

Public Property Get Enabled() As Boolean
Public Property Let Enabled(ByVal Value As Boolean)

Returns/sets whether the object can respond to user events.

OLEDragMode

Public Property Get OLEDragMode() As VBRUN.OLEDragConstants
Public Property Let OLEDragMode(ByVal Value As VBRUN.OLEDragConstants)

Returns/sets the OLE drag mode.

OLEDropMode

Public Property Get OLEDropMode() As OLEDropModeConstants
Public Property Let OLEDropMode(ByVal Value As OLEDropModeConstants)

Returns/sets whether the object can act as an OLE drop target.

MousePointer

Public Property Get MousePointer() As CCMousePointerConstants
Public Property Let MousePointer(ByVal Value As CCMousePointerConstants)

Returns/sets the pointer type displayed when the mouse hovers. See common enumerations.

MouseIcon

Public Property Get MouseIcon() As IPictureDisp
Public Property Let MouseIcon(ByVal Value As IPictureDisp)
Public Property Set MouseIcon(ByVal Value As IPictureDisp)

Returns/sets the custom mouse icon.

MouseTrack

Public Property Get MouseTrack() As Boolean
Public Property Let MouseTrack(ByVal Value As Boolean)

Returns/sets whether events are triggered when the mouse enters or leaves the control.

RightToLeft

Public Property Get RightToLeft() As Boolean
Public Property Let RightToLeft(ByVal Value As Boolean)

Returns/sets the right-to-left display direction.

RightToLeftMode

Public Property Get RightToLeftMode() As CCRightToLeftModeConstants
Public Property Let RightToLeftMode(ByVal Value As CCRightToLeftModeConstants)

Returns/sets the right-to-left mode. See common enumerations.

Style

Public Property Get Style() As VcbStyleConstants
Public Property Let Style(ByVal Value As VcbStyleConstants)

Returns/sets the combo box style. Can only be set at design time.

Locked

Public Property Get Locked() As Boolean
Public Property Let Locked(ByVal Value As Boolean)

Returns/sets whether the control is locked (prevents editing and selection).

Text

Public Property Get Text() As String
Public Property Let Text(ByVal Value As String)

Returns/sets the edit box text.

Default

Public Property Get Default() As String
Public Property Let Default(ByVal Value As String)

Returns/sets the default text.

ExtendedUI

Public Property Get ExtendedUI() As Boolean
Public Property Let ExtendedUI(ByVal Value As Boolean)

Returns/sets whether extended user interface is used (F4 key opens drop-down, ESC key closes).

MaxDropDownItems

Public Property Get MaxDropDownItems() As Integer
Public Property Let MaxDropDownItems(ByVal Value As Integer)

Returns/sets the maximum number of items displayed in the drop-down list.

IntegralHeight

Public Property Get IntegralHeight() As Boolean
Public Property Let IntegralHeight(ByVal Value As Boolean)

Returns/sets whether the height is adjusted to show complete items. Can only be set at design time.

MaxLength

Public Property Get MaxLength() As Long
Public Property Let MaxLength(ByVal Value As Long)

Returns/sets the maximum text length in the edit box.

UseListBackColor

Public Property Get UseListBackColor() As Boolean
Public Property Let UseListBackColor(ByVal Value As Boolean)

Returns/sets whether to use the list background color.

UseListForeColor

Public Property Get UseListForeColor() As Boolean
Public Property Let UseListForeColor(ByVal Value As Boolean)

Returns/sets whether to use the list foreground color.

ListBackColor

Public Property Get ListBackColor() As OLE_COLOR
Public Property Let ListBackColor(ByVal Value As OLE_COLOR)

Returns/sets the drop-down list background color.

ListForeColor

Public Property Get ListForeColor() As OLE_COLOR
Public Property Let ListForeColor(ByVal Value As OLE_COLOR)

Returns/sets the drop-down list foreground color.

HorizontalExtent

Public Property Get HorizontalExtent() As Single
Public Property Let HorizontalExtent(ByVal Value As Single)

Returns/sets the horizontal scroll range of the drop-down list.

DrawMode

Public Property Get DrawMode() As VcbDrawModeConstants
Public Property Let DrawMode(ByVal Value As VcbDrawModeConstants)

Returns/sets the draw mode. Can only be set at design time.

IMEMode

Public Property Get IMEMode() As CCIMEModeConstants
Public Property Let IMEMode(ByVal Value As CCIMEModeConstants)

Returns/sets the input method editor mode. See common enumerations.

ScrollTrack

Public Property Get ScrollTrack() As Boolean
Public Property Let ScrollTrack(ByVal Value As Boolean)

Returns/sets whether scroll tracking is enabled (real-time scrolling while dragging the thumb).

AutoSelect

Public Property Get AutoSelect() As Boolean
Public Property Let AutoSelect(ByVal Value As Boolean)

Returns/sets whether to automatically select matching items.

AlwaysFindExact

Public Property Get AlwaysFindExact() As Boolean
Public Property Let AlwaysFindExact(ByVal Value As Boolean)

Returns/sets whether to always perform exact find.

ListCount

Public Property Get ListCount() As Long

Returns the number of list items.

List

Public Property Get List(ByVal Index As Long) As String

Gets the list item text at the specified index. Data is obtained through the GetVirtualItem event.

ListIndex

Public Property Get ListIndex() As Long
Public Property Let ListIndex(ByVal Value As Long)

Returns/sets the currently selected item index.

SelStart

Public Property Get SelStart() As Long
Public Property Let SelStart(ByVal Value As Long)

Returns/sets the selection start position.

SelLength

Public Property Get SelLength() As Long
Public Property Let SelLength(ByVal Value As Long)

Returns/sets the selection length.

SelText

Public Property Get SelText() As String
Public Property Let SelText(ByVal Value As String)

Returns/sets the selected text.

ItemHeight

Public Property Get ItemHeight() As Single
Public Property Let ItemHeight(ByVal Value As Single)

Returns/sets the item height.

FieldHeight

Public Property Get FieldHeight() As Single

Returns the edit box height.

DroppedDown

Public Property Get DroppedDown() As Boolean
Public Property Let DroppedDown(ByVal Value As Boolean)

Returns/sets whether the control is in a dropped-down state.

DropDownWidth

Public Property Get DropDownWidth() As Single
Public Property Let DropDownWidth(ByVal Value As Single)

Returns/sets the drop-down list width.

DropDownHeight

Public Property Get DropDownHeight() As Single
Public Property Let DropDownHeight(ByVal Value As Single)

Returns/sets the drop-down list height.

TopIndex

Public Property Get TopIndex() As Long
Public Property Let TopIndex(ByVal Value As Long)

Returns/sets the index of the top visible item in the drop-down list.

Methods

OLEDrag

Public Sub OLEDrag()

Initiates an OLE drag-drop operation.

Drag

Public Sub Drag(Optional ByRef Action As Variant)

Starts, ends, or cancels a drag operation.

SetFocus

Public Sub SetFocus()

Moves focus to the specified object.

ZOrder

Public Sub ZOrder(Optional ByRef Position As Variant)

Sets the Z-order.

Refresh

Public Sub Refresh()

Forces a complete redraw of the object.

FindItem

Public Function FindItem(ByVal Text As String, Optional ByVal Index As Long = -1, Optional ByVal Partial As Boolean) As Long

Finds a list item. Returns the matching item index, or -1 if not found.

GetIdealHorizontalExtent

Public Function GetIdealHorizontalExtent() As Single

Gets the ideal horizontal scroll range.

SelectItem

Public Function SelectItem(ByVal Text As String, Optional ByVal Index As Long = -1) As Long

Searches for and selects a matching list item. Returns the selected item index.

Events

Click

Public Event Click()

Fired when the user clicks the control.

DblClick

Public Event DblClick()

Fired when the user double-clicks the control.

Scroll

Public Event Scroll()

Fired when the drop-down list scrolls.

Change

Public Event Change()

Fired when the text content changes.

ContextMenu

Public Event ContextMenu(ByRef Handled As Boolean, ByVal X As Single, ByVal Y As Single)

Context menu event. Set Handled to True to suppress the default menu.

GetVirtualItem

Public Event GetVirtualItem(ByVal Item As Long, ByRef Text As String)

Fired when virtual item data is requested. Set the Text parameter to return the item text.

FindVirtualItem

Public Event FindVirtualItem(ByVal StartIndex As Long, ByVal SearchText As String, ByVal Partial As Boolean, ByRef FoundIndex As Long)

Fired when searching for a virtual item. Set FoundIndex to return the matching item index, or -1 if not found.

IncrementalSearch

Public Event IncrementalSearch(ByVal SearchString As String, ByVal StartIndex As Long, ByRef FoundIndex As Long)

Fired during incremental search. Set FoundIndex to return the matching item index.

DropDown

Public Event DropDown()

Fired when the drop-down list expands.

CloseUp

Public Event CloseUp()

Fired when the drop-down list closes.

ItemDraw

Public Event ItemDraw(ByVal Item As Long, ByVal ItemAction As Long, ByVal ItemState As Long, ByVal hDC As Long, ByVal Left As Long, ByVal Top As Long, ByVal Right As Long, ByVal Bottom As Long)

Fired when drawing an owner-draw item (when DrawMode is OwnerDrawFixed).

PreviewKeyDown

Public Event PreviewKeyDown(ByVal KeyCode As Integer, ByRef IsInputKey As Boolean)

Preview key event. Set IsInputKey to True to mark the key as an input key.

PreviewKeyUp

Public Event PreviewKeyUp(ByVal KeyCode As Integer, ByRef IsInputKey As Boolean)

Preview key up event.

KeyDown

Public Event KeyDown(KeyCode As Integer, Shift As Integer)

Fired when a keyboard key is pressed.

KeyUp

Public Event KeyUp(KeyCode As Integer, Shift As Integer)

Fired when a keyboard key is released.

KeyPress

Public Event KeyPress(KeyChar As Integer)

Fired when an ANSI key is pressed and released.

MouseDown

Public Event MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

Fired when a mouse button is pressed.

MouseMove

Public Event MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)

Fired when the mouse is moved.

MouseUp

Public Event MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)

Fired when a mouse button is released.

MouseEnter

Public Event MouseEnter()

Fired when the mouse enters the control area.

MouseLeave

Public Event MouseLeave()

Fired when the mouse leaves the control area.

OLECompleteDrag

Public Event OLECompleteDrag(Effect As Long)

Fired when an OLE drag-drop operation completes.

OLEDragDrop

Public Event OLEDragDrop(Data As DataObject, Effect As Long, Button As Integer, Shift As Integer, X As Single, Y As Single)

Fired when data is dropped in an OLE drag-drop operation.

OLEDragOver

Public Event OLEDragOver(Data As DataObject, Effect As Long, Button As Integer, Shift As Integer, X As Single, Y As Single, State As Integer)

Fired when the mouse hovers during an OLE drag-drop operation.

OLEGiveFeedback

Public Event OLEGiveFeedback(Effect As Long, DefaultCursors As Boolean)

Fired when feedback is given during an OLE drag-drop operation.

OLESetData

Public Event OLESetData(Data As DataObject, DataFormat As Integer)

Fired when data is set during an OLE drag-drop operation.

OLEStartDrag

Public Event OLEStartDrag(Data As DataObject, AllowedEffects As Long)

Fired when an OLE drag-drop operation starts.

Helper Module

VirtualComboBase.bas

Custom window class helper module that registers/unregisters the "VComboBoxWndClass" window class and adds the LBS_NODATA style to ComboLBox.

VcbWndRegisterClass

Public Sub VcbWndRegisterClass()

Registers the custom window class.

VcbWndReleaseClass

Public Sub VcbWndReleaseClass()

Unregisters the custom window class.

Code Examples

Basic Usage

' Set up virtual combo box
With VirtualCombo1
    .Style = VcbStyleDropDownList
    .ListCount = 1000
    .MaxDropDownItems = 15
End With

' Provide virtual item data
Private Sub VirtualCombo1_GetVirtualItem(ByVal Item As Long, ByRef Text As String)
    Text = "Item " & CStr(Item)
End Sub

' Find virtual item
Private Sub VirtualCombo1_FindVirtualItem(ByVal StartIndex As Long, _
    ByVal SearchText As String, ByVal Partial As Boolean, ByRef FoundIndex As Long)
    FoundIndex = -1
End Sub

' Listen for drop-down event
Private Sub VirtualCombo1_DropDown()
    Debug.Print "Drop-down list opened"
End Sub

Private Sub VirtualCombo1_Change()
    Debug.Print "Current text: " & VirtualCombo1.Text
End Sub