The DropDownTree controls contains an Embedded TreeView control, which you need to use, in order to access the Nodes (loop all items) and use it to set certain node from the NodesCollection as selected.
In addition, in order to apply this selection to the DropDownTree, you need to call the SyncEmbeddedTree()
method on the DropDownTree.
In the attachment you can find a sample example, demonstrating the above suggested approach.
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