Well, LoadXmlString is not working with the binding mechanism. It has a separate implementation. The ID is mapped either to the ID property of the node, or it's in the Attributes collection (where all not-having-representation-in-the-property-bag of RadTreeNode properties go).
As you stated the first solution will work for this scenario. What is the problem using the dataSource instead?
If you are not able the use the first one, please, specify the reasons (you can share the requirements that you try and are not to implement this way) for that.
Hope that soon we will resolve this!
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