Sorry Roi if you if you do vartype you will get an error but if you do TYPE has I said then if the SelectKey is invalid type will return U so try the following:

IF TYPE('This.Nodes[SelectedKey]') = 'O'
   This.SelectedItem = This.Nodes[SelectedKey]
ENDIF

>Nope, This.Nodes is a method that returns an object. The SelectedKey is just a string for the index key. If the index key references a non existant node an error occurs. That's my problem. I need to know if the object exists in the collection prior to calling This.Nodes.
>
>>Roi and how about TYPE('This.Nodes[SelectedKey]') This should work.
>>
>>>Same deal, This.Nodes[SelectedKey] causes and error. I think I just have to catch the error and go from there.
>>>
>>>>Sorry try this one:
>>>>>I have a method that rebuilds all the nodes in a treeview.
>>>>>
>>>>>I save the currently selected node with:
>>>>>

SelectedKey = This.SelectedItem.Key

>>>>>
>>>>>Then I clear all the nodes and rebuild the tree.
>>>>>
>>>>>Then I want to reselect the Selected item with:
>>>>>

This.SelectedItem = This.Nodes[SelectedKey]
>>>>>This.SelectedItem.ensurevisible

>>>>>
>>>>>However sometimes the SelectedKey doesn't exist once the tree is rebuilt. Is there an easy way to determine that? I can't spin through all the keys because I build each branch dynamically as it is expanded. The only thing I've can think of is setting it, catching the error if it doesn't exist, and going on from there.
>>>>>
>>>>>tia