Gets or sets the path to a Boolean value on the source node item to serve as the expansion indicator in the hierarchical collection, or null to indicate that the expansion indicator is not provided by the source node item. If a parent node is expanded its child nodes become visible. If a parent node is collapsed its child nodes become invisible. This is a dependency property.

[BindableAttribute(true)]
public string IsExpandedMemberPath { get; set; }

<BindableAttribute(True)> _
Public Property IsExpandedMemberPath As String