TDBLookupComboBox class

In unit DBCtrls

TDBLookupComboBox is a data-aware combo-box for examining a lookup table in a database.

Declaration

pascal

TDBLookupComboBox = class(TCustomDBComboBox)

Inheritance

Description

TDBLookupComboBox is a TCustomDBComboBox descendant which implements a data-aware combo-box control that adds lookup capabilities using values from a separate dataset. Like the ancestor class, the DataField and DataSource properties are used to identify the dataset and field where the selected value for the control is stored. The ListSource, KeyField, and ListField properties are added to define the dataset with the values displayed and captured using the drop down for the combo-box control. Internally, a TDBLookUp instance is used to perform lookup operations for the control.

Other important properties used to manage the behavior and appearance of the control include:

AutoComplete
AutoDropDown
AutoSelect
NullValueKey
EmptyValue
DisplayEmpty
ScrollListDataset

Properties

`KeyValue`	public	Value for the key field in the lookup dataset at the position in ItemIndex.
`DropDownCount`	public	Deprecated. Use DropDownRows instead.
`Align`	published	Specifies the placement of the control on its Parent control.
`Anchors`	published	The set of anchor definitions for this control.
`ArrowKeysTraverseList`	published	Indicates if keyboard Arrow (or cursor) keys can be used to move through the list.
`AutoComplete`	published	Positions the list box using partial text matching.
`AutoDropDown`	published	Makes the drop-down list appear as soon as the user starts entering text.
`AutoSelect`	published	Selects the entire content of the edit box when the control receives the focus.
`AutoSize`	published	Allows automatic adjustment of the size for the control, according to its content.
`BiDiMode`	published	Indicates whether text controls use in bi-directional reading.
`BorderSpacing`	published	Determines the inner and outer border spacing for this control.
`BorderStyle`	published	Indicates the border style displayed around the control.
`CharCase`	published	Indicates the case conversion applied to the value entered in the edit box for the control.
`Color`	published	The background color for the control.
`Constraints`	published	Contains the minimum and maximum Width and Height for the control.
`DataField`	published	The name of the Field which provides the values displayed in the control.
`DataSource`	published	Provides access to the dataset with content for the control.
`DoubleBuffered`	published	When enabled, it reduces flicker when the control is painted.
`DragCursor`	published	The cursor shape shown during a drag operation.
`DragKind`	published	Indicates the action performed for a drag operation: drag-and-drop or drag-and-dock.
`DragMode`	published	Determines how a drag operation is started for the control.
`DropDownRows`	published	Number of rows displayed in the drop-down list for the control.
`Enabled`	published	Determines whether the control responds to mouse or keyboard input.
`Font`	published	The font to be used for text display in this control.
`ItemWidth`	published	The minimum width of the items in the drop-down list.
`KeyField`	published	KeyField the name of the field containing the key data.
`ListField`	published	ListField is the name of the field containing the list data displayed in the control.
`ListFieldIndex`	published	ListFieldIndex - the index value of the field containing the list.
`ListSource`	published	ListSource the data source that contains the list.
`LookupCache`	published	Indicates if look-up items are cached in the field data link for the control.
`NullValueKey`	published	Keyboard shortcut which causes an empty value to be assigned to the field value for the lookup control.
`EmptyValue`	published	Value stored for the lookup control when a lookup value is not available.
`DisplayEmpty`	published	Value displayed in the lookup control when a lookup value is not available.
`ParentBiDiMode`	published	Indicates whether the BiDiMode settings in the Parent control are used.
`ParentColor`	published	Use the Color from the Parent control, when enabled.
`ParentDoubleBuffered`	published	Value for the DoubleBuffered property in a Parent control.
`ParentFont`	published	Indicates if the Font from the Parent control is used in the control.
`ParentShowHint`	published	If True, the value of ShowHint for the control will be the same as the one from the Parent. Default is True.
`PopupMenu`	published	A context-sensitive menu that pops up when the right mouse button is clicked over this control.
`ReadOnly`	published	Disallows free-form entry of Text into the combo-box edit field.
`ScrollListDataset`	published	Indicates if the Dataset in ListSource can be scrolled when loading/locating key and display values.
`ShowHint`	published	Enables Hint display for the control.
`Sorted`	published	Determines whether the list entries are sorted in alphanumeric order.
`Style`	published	Controls the appearance and behavior for the combo-box.
`TabOrder`	published	Indicates the navigation order for the control when the user presses the Tab or Shift+Tab key.
`TabStop`	published	Allows the user to navigate to / from the control by pressing the Tab or Shift+Tab keys.
`Visible`	published	Allows the control, and all of its children, to be displayed or hidden.

Methods

`DefineProperties`	protected	Defines read and write routines for properties values in the class instance.
`DoEdit`	protected	Implements support for the "unbound" editing mode in the data-aware control.
`DoAutoCompleteSelect`	protected	Ensures the internal TDBLookup instance is updated when the control is used in "unbound" mode.
`IsUnbound`	protected	Indicates if the control lacks a datasource or field name ("unbound" mode).
`InitializeWnd`	protected	Ensures that the lookup uses the address for the items defined in the control.
`DestroyWnd`	protected	Updates the lookup with the address for the items in the control when the control handle is freed.
`KeyDown`	protected	Handles the Null key shortcut in key down events.
`UTF8KeyPress`	protected	Handles UTF-8 characters for the data-aware control.
`Loaded`	protected	Performs actions when a component has been loaded during LCL streaming.
`UpdateData`	protected	UpdateData - copies the local data from the corresponding entry from the lookup field.
`DataChange`	protected	Updates the control when the value in the linked dataset has been changed.
`DoOnSelect`	protected	Performs the OnSelect event handler when in drop-down list mode.
`Create`	public	Constructor for the class instance.

Events

`OnChange`	published	Event handler signalled for user changes to the text in the edit box.
`OnChangeBounds`	published	Event handler signalled when the Bounds for the control have been changed.
`OnClick`	published	Notification handler for mouse clicks.
`OnCloseUp`	published	Handler invoked when the drop-down list closes.
`OnContextPopup`	published	Invoked when a context-sensitive pop-up menu is requested.
`OnDblClick`	published	Event handler signalled when a mouse double click occurs in the control.
`OnDragDrop`	published	Event handler signalled when an object is dropped onto the control.
`OnDragOver`	published	Event handler signalled when a control is dragged over the control instance.
`OnDrawItem`	published	Handler for special painting of an item (in owner-draw mode).
`OnDropDown`	published	Handler invoked when the list has dropped down.
`OnEditingDone`	published	Event handler signalled when editing is completed for the control.
`OnEndDrag`	published	Event handler signalled for the end of a drag-drop operation.
`OnEnter`	published	Event handler signalled when the control receives focus.
`OnExit`	published	Event handler signalled when the control loses focus.
`OnKeyDown`	published	Event handler signalled for key down keyboard events.
`OnKeyPress`	published	Event handler signalled for character data entered by the user.
`OnKeyUp`	published	Event handler signalled when a key up event has occurred for the control.
`OnMouseDown`	published	Event handler signalled when a mouse down event is handled for the control.
`OnMouseEnter`	published	Event handler signalled when the mouse pointer has entered the control.
`OnMouseLeave`	published	Event handler signalled when the mouse pointer has left the control.
`OnMouseMove`	published	Event handler signalled when the mouse pointer is moved in the control.
`OnMouseUp`	published	Event handler signalled when a mouse up event is handled for the control.
`OnMouseWheel`	published	Event handler for mouse wheel turned.
`OnMouseWheelDown`	published	Event handler signalled for a downward movement of the mouse wheel.
`OnMouseWheelUp`	published	Event handler signalled for an upward movement of the mouse wheel.
`OnSelect`	published	Handler invoked when an item is selected.
`OnStartDrag`	published	Event handler signalled for the start of a dragging operation.
`OnUTF8KeyPress`	published	Handler for a character entered by the user.