ComboBox

Inheritance Hierarchy

Description

The ComboBox component combines functions of the ListBox and EditBox components.

Working with the Component

The component enables the user to select a value in the list or set a custom value.

The difference of the ComboBox from the similar ListBox component is the following:

ComboBox allows the user to enter his own values.
ComboBox can be expanded as well as collapsed (ListBox is always expanded).
ComboBox does not allow multiple selection.

The main property of the component is Items. This list can be filled when a form is being developed (designed). To do this, click a button with ellipsis next to the property in the Objects Inspector window or select the Elements item in the component's context menu.

The main event of the OnChange component occurs when a text in the edit window is changed as a result of direct editing or selecting in the list.

Component style depends on the Style property.

The user choice or the text entered by the user can be determined by the value of the Text property.

The index of the element selected by the user can be determined by the value of the ItemIndex property.

Example

Properties of the ComboBox Component

	Property name	Brief description
	Align	The Align property determines behavior of the component when its parent component is resized.
	AllowDrag	The AllowDrag property determines whether an object can be dragged from the component.
	AllowDrop	The AllowDrop property determines whether the component can accept a dragged object.
	Anchors	The Anchors property returns settings that determine the percentage of the size change for the current component when the parent component is resized.
	Brush	The Brush property determines the brush that is used to fill component area.
	ClientHeight	The ClientHeight property is used to receive or specify the height of the component’s client area.
	ClientWidth	The ClientWidth property is used to receive or specify the width of the component’s client area.
	Color	The Color property determines a component background color.
	ComponentCount	The ComponentCount property returns the number of child components.
	Components	The Components property returns the child component.
	Cursor	The Cursor property determines the look of the cursor over the component.
	Data	The Data property is used to store any custom data.
	DropDownCount	The DropDownCount property determines the maximum number of elements simultaneously displayed in a drop-down list.
	DroppedDown	The DroppedDown property returns True if the drop-down list of the component is expanded.
	Enabled	The Enabled property determines whether the component is available for the user.
	Focused	The Focused property returns True if the focus is set on the component.
	Font	The Font property determines the set of characteristics describing the font that is used to display text.
	Height	The Height property determines component height.
	HelpContext	The HelpContext property determines a unique index for the context help section for this component.
	Hint	The Hint property determines a component tooltip text.
	ItemCount	The ItemCount property returns the number of rows in a drop-down list.
	ItemHeight	The ItemHeight property returns the height of elements (rows) of a drop-down list.
	ItemIndex	The ItemIndex property determines the index of the selected list element.
	Items	The Items property returns the drop-down list rows collection.
	Left	The Left property determines the coordinate of the left border of the component.
	MaxLength	The MaxLength property determines the maximum length of the entered text.
	Name	The Name property determines a component name.
	Parent	The Parent property determines a parent component.
	ParentColor	The ParentColor property determines whether the component inherits the color of the parent component.
	ParentFont	The ParentFont property determines whether the component uses the font of the parent component.
	ParentShowHint	The ParentShowHint property determines whether a tooltip is displayed.
	PopupMenu	The PopupMenu property determines the context menu opened by clicking the component with the additional mouse button.
	Scrolls	The Scrolls property returns parameters of component's scrollbars.
	SelLength	The SelLength property determines the number of characters selected in the component text.
	SelStart	The SelStart property determines the cursor position, from which to start text selection in the component.
	SelText	The SelText property determines the text selected in the component.
	ShowHint	The ShowHint property enables and disables showing a component tooltip.
	Sorted	The Sorted property determines whether the rows in the drop-down list must be automatically sorted in alphabetical order.
	Style	The Style property determines a style of displaying drop-down list.
	TabOrder	The TabOrder property determines the component position in the tab order.
	TabStop	The TabStop property determines whether the component is focused when the TAB key is pressed.
	Tag	The Tag property is not used by the compiler. The user can change the value of the Tag property and use it as he wishes.
	Text	The Text property determines the row identifying a component for the user.
	Top	The Top property determines the coordinate of the top border of the component.
	Visible	The Visible property determines visibility of the component during execution.
	Width	The Width property determines component width.

Methods of the ComboBox Component

	Method name	Brief description
	BringToFront	The BringToFront method brings a component to front.
	ClearEdit	The ClearEdit method clears the component edit box.
	ClientToScreen	The ClientToScreen method converts the coordinates of a point specified relative to the component coordinate system into screen coordinates.
	DoDragDrop	The DoDragDrop method enables to start dragging operation.
	GetImage	The GetImage method returns the image of the component with all the child components.
	SelectAll	The SelectAll method selects all component text in the component edit box.
	ScreenToClient	The ScreenToClient method converts screen coordinates of a point into coordinates specified relative to the component coordinate system.
	SendToBack	The SendToBack method sends a component to back.
	SetFocus	The SetFocus method sets focus to this component.

Events of the ComboBox Component

	Event name	Brief description
	OnBeginDrag	The OnBeginDrag event occurs for a component when the user starts to drag an object from the component.
	OnChange	The OnChange event occurs when the text in the component edit box is changed.
	OnClick	The OnClick event occurs if the user clicks the component area.
	OnDblClick	The OnDblClick event occurs if the user double-clicks the component area.
	OnDragDrop	The OnDragDrop event occurs for the component if the user drops a dragged object over it.
	OnDragEnter	The OnDragEnter event occurs when a dragged object crosses the borders of this component.
	OnDragLeave	The OnDragLeave event occurs when a dragged object leaves the borders of this component.
	OnDragOver	The OnDragOver event occurs for the component when the user drags an object over it.
	OnDropDown	The OnDropDown event occurs when a drop-down list is displayed.
	OnEnter	The OnEnter event occurs when the component receives focus.
	OnExit	The OnExit event occurs when the component loses focus.
	OnHScroll	The OnHScroll event occurs when horizontal scrollbar slider changes its position.
	OnItemSelect	The OnItemSelect event occurs when an element is selected from the list.
	OnKeyDown	The OnKeyDown event occurs if the component is focused and a keyboard key is pressed.
	OnKeyPress	The OnKeyPress event occurs if the component is focused when the user presses a character key.
	OnKeyPreview	The OnKeyPreview event occurs prior to each event related to key pressing.
	OnKeyUp	The OnKeyUp event occurs if the component is focused and the user releases any button previously pressed.
	OnMouseDown	The OnMouseDown event occurs if the pointer is in component's area and a mouse key is pressed.
	OnMouseEnter	The OnMouseEnter event occurs when mouse cursor enters the component area.
	OnMouseHover	The OnMouseHover event occurs when mouse cursor is held in the component area.
	OnMouseLeave	The OnMouseLeave event occurs when mouse cursor leaves the component area.
	OnMouseMove	The OnMouseMove event occurs on moving the cursor over component.
	OnMouseUp	The OnMouseUp event occurs on releasing mouse button when the cursor is in component area.
	OnMouseWheel	The OnMouseWheel event occurs if the component is focused when the mouse wheel is rotated.
	OnVScroll	The OnVScroll event occurs when vertical scrollbar slider changes its position.