If a diagram represents a tree structure, the tree branch starting from a node can be collapsed or expanded in order to hide or display hierarchy details. Use the nodes' Collapse and Expand methods to do this programmatically. To determine whether a sub-tree is expanded or collapsed, check its root's Expanded property.
Displaying Expand/Collapse Button
If the
Expandable property of a node is set to
true, there is a +/- button displayed beside the node to allow users to collapse or expand the tree branch starting there. The button location can be customized by the diagram's
ExpandButtonPosition property. By default, pressing that button calls automatically the
Collapse and
Expand methods and raises the
TreeExpanded or
TreeCollapsed events.
Defining Tree Direction
A node can be connected to other nodes through outgoing and incoming links. Setting the
ExpandOnIncoming property specifies which items connected to a node will be regarded as its descendants. If
ExpandOnIncoming is
false (default value), then each node will be regarded as a parent of its outgoing links and the items attached to them. If
ExpandOnIncoming is set to
true, the node's incoming links define its children. So that property specifies the direction of parent-children relationship between diagram items and respectively the overall direction in which collapsing / expanding is done.
Expanding a Branch Recursively
Use the
RecursiveExpand property to specify whether the whole tree branch starting from a node will be shown when expanding, or only the first level of descendants. A related property is the
Expandable property of the
Group class which specifies whether expanding and collapsing propagate through group members.
HtmlBuilder Support
The
HtmlBuilder class can generate map areas for the +/- buttons displayed beside
Expandable nodes. To enable that, assign an URL to the
ExpandBtnHyperLink property. That URL can contain some format specifiers which are automatically replaced by the values of nodes'
Tag or
ZIndex properties. You can identify on the server side the node whose +/- button is clicked.
