[Overview][Types][Classes][Procedures and functions][Index] | Reference for unit 'CheckLst' (#lcl)

# TCustomCheckListBox.OnClickCheck

Event handler signalled when a check box in the control has been changed.

## Declaration

Source position: checklst.pas line 86

`public property TCustomCheckListBox.OnClickCheck : TNotifyEvent read FOnClickCheck write FOnClickCheck;`

## Description

OnClickCheck is a TNotifyEvent property with the event handler signalled when the check box state for one of the list items has been changed.

Applications must implement and assign a procedure using the TNotifyEvent signature to respond to the notification. The Sender argument contains the TCheckListBox instance for the notification, and allows access to its properties and methods.

OnClickCheck is signalled (when assigned) from the ClickCheck method. ClickCheck is called from methods like DoChange (private) and KeyDown. This causes OnClickCheck to be signalled when the mouse is clicked on a check box, and when the value for the current item is Toggled using the Space key.

OnClickCheck is signalled before other event handlers like OnItemClick, OnSelectionChange, and OnClick.

OnClickCheck and OnItemClick are not signalled when the checked state for an item is changed in code using Checked, State, CheckAll, or Toggle.

Use OnItemClick for the event signalled with the item index for the affected check box in the control.

## See also

TCustomCheckListBox.ClickCheck |  | Performs actions needed when a value in the control is about to change.
TCustomCheckListBox.KeyDown |  | Handles key down messages for the control.
TCustomCheckListBox.OnItemClick |  | Deprecated. Event handler signalled when the check box state for a specific item has been changed.
TCustomListBox.OnSelectionChange |  | Handler invoked when an item is selected in the control.
TCustomListBox.OnClick |  | Notification handler for mouse clicks.
TNotifyEvent