TCustomDBComboBox class

In unit DBCtrls

TCustomDBComboBox is a data-aware combo-box for displaying information from a database.

Declaration

pascal

TCustomDBComboBox = class(TCustomComboBox)

Inheritance

Descends from it: TDBComboBox TDBLookupComboBox

Description

TCustomDBComboBox is a TCustomComboBox descendant which specifies a data-aware combo-box control used to display and edit values in a database table. TCustomDBComboBox extends the ancestor class to provide DataField, DataSource, and Field properties needed to control access to the field in a linked dataset.

Methods are provided which enable the database features for the control, and maintain the interaction between the control and the underlying dataset. Internally, a TFieldDataLink class instance is used to maintain the association between the control and it data source and field.

TCustomDBComboBox is used as the ancestor for the TDBComboBox and TDBLookupComboBox controls. Do not create instances of TCustomDBComboBox; use one of the descendent classes.

Properties

`DetectedEvents`	protected	Deferred messages pending for the control.
`Field`	public	Contains the field definition from the linked dataset.
`Text`	public	The value in the edit box for the control.
`ItemIndex`	public	The index of the currently selected item, or -1 if no item is selected.
`DataField`	public	The name of the Field which provides the values displayed in the control.
`DataSource`	public	Provides access to the dataset with content for the control.
`ReadOnly`	public	Indicates if the control is prevented from changing the field value in its linked dataset.

Methods

`DoEdit`	protected	Performs LCL deferred edit messages for events detected in the control.
`DoOnCloseUp`	protected	Performs actions to close the drop down for the combo-box.
`DoOnSelect`	protected	Calls Select to trigger the OnSelect event handler.
`DoOnChange`	protected	Calls Change to trigger the OnChange event handler.
`LMDeferredEdit`	protected	Implements the LCL message for a deferred edit.
`CloseUp`	protected	Sets deferred events when the drop down for the combo-box is closed.
`Select`	protected	Checks for the DBCBEVENT_SELECT message in the control.
`DataChange`	protected	DataChange - updates any changes in text.
`DoMouseWheel`	protected	Checks for mouse wheel events in the control.
`Notification`	protected	Notification handler for insertion or deletion of components.
`Change`	protected	Change -if there has been a change to the data the link must be notified.
`KeyDown`	protected	Performs actions needed to apply the key down event.
`UpdateData`	protected	UpdateData - implements any pending changes in the data.
`UpdateRecord`	protected	Updates the record in the linked dataset with the value for the control.
`WndProc`	protected	Handles cut, copy and paste window messages for the control.
`Create`	public	Constructor for the class instance.
`Destroy`	public	Destructor for the class instance.
`ExecuteAction`	public	Provides support for TBasicAction in the control.
`UpdateAction`	public	Updates the specified action to reflect the current state in the linked dataset.
`EditingDone`	public	Updates data through the link, then calls inherited EditingDone.