In addition to bound and unbound modes, the TreeList extension can operate in a Virtual Mode, which greatly reduces both the server load and start-up time when working with complex or dynamically created data. In a virtual mode, a tree is created on demand. In this instance, child nodes are created and initialized when their parent node is expanded.
To implement a virtual mode for the TreeList extension, a specifically parameterized BindToVirtualData method can be used. The method's parameters refer to delegate methods that can be declared as static methods within a model class. Within the first delegate method, create a list of business objects that correspond to the child nodes owned by the processed node. The second one enables you to specify the node's key value and cell values.
In this demo, the TreeList extension uses this data binding method to display the file/folder tree of this demo's website.