Gets or sets the value that root nodes contain in the field specified by the ASPxTreeList.ParentFieldName property.
An object that represents the root value.
By default, if a node's parent field value doesn't point to any other node, the node is added to the collection of root nodes (ASPxTreeList.Nodes).
However, if you specify the RootValue property's value, only those nodes whose parent field value matches RootValue are added to the collection of root nodes. If the node's parent field value doesn't match RootValue, and doesn't point to any other node, this node isn't displayed within the ASPxTreeList.
To learn more, see Tree Generation Algorithm in the ASPxTreeList.