TShellTreeView.OnExpanding property

Declaration

property OnExpanding: ;

Description

Not described here; this is what TCustomTreeView.OnExpanding says of it:

Event handler signalled prior to expanding a node on the tree view control.

OnExpanding is a TTVExpandingEvent property with the event handler signalled before a tree node is expanded on the tree view control. It is signalled (when assigned) from the CanExpand method, and allows the application to perform actions needed before the tree node is expanded to reveal its child nodes.

Arguments for the event handler include:

Sender

Object instance (TCustomTreeView) for the event.

Node

The TTreeNode instance to be expanded on the tree view control.

AllowExpansion

Boolean variable argument which indicates whether the tree node can be expanded on the control. Set AllowExpansion to False to prevent expansion of the tree node.

OnExpanding is not signalled if the tree node does not have any child nodes (HasChildren is False).

Use OnExpanded to perform actions needed after a tree node has been expanded on the control.

Use OnCollapsing and OnCollapsed to perform actions before or after a node is collapsed on the tree view control.