[Solved] Index was out of range. ... error on TreeView after attempting to expand a second node on demand...

[Peter From LA]

We are using a RAD treeView in our application that was built couple of years ago and curently we are trying to convert to Prometheus. It expands its nodes on demand (client-side). The first expansion works like a charm, but the expansion of a second node (child or peer to the first one, it does not matter) gives me this alert message:
"Index was out of range. Must be non-negative and less than..."

Also I noticed that the second call never reaches the server-side event handler - the same one that worked fine while building the expansion of the first node.

Any ideas hos to overcome this?

[Veselin Vasilev]

Hi Peter Kalev,

When you add TreeNodes on the client-side (via ExpandMode.ServerSideCallBack), you should take into account that the nodes are not persisted on the server-side. Therefore, the nodes added this way cannot take part in any server-side events. Also, you cannot access the nodes on the server-side and change their properties. The nodes are accessible only on the client-side and can take part only in client-side events.

If you need to persist the expanded state of the TreeNodes after a postback, you can use the approach described in the following article:

Storing the expanded state of TreeNodes added via callback

If you need to access the nodes on the server-side, then you should definitely use ExpandMode.ServerSide. Furthermore, you can wrap the treeview with an AJAX Panel (Telerik RadAjax) that will transform each postback into a callback. Thus you will keep the needed client-side behavior.

All the best,
Veskoni
the Telerik team

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[Peter From LA]

Well... If I have a TreeView and I click to expand a node on demand, I would not expect any magic needs to be performed to open a second node on demand, especially if the second node is a peer to the first one. Also the example on your web site works fine without the techniques you are suggesting.

[Veselin Vasilev]

Hello Peter Kalev,

I think the best way to proceed is to open a formal support ticket and attach a sample project to it.
So we can test it locally and find a working solution for you.

Thanks

Regards,
Veskoni
the Telerik team

Instantly find answers to your questions at the new Telerik Support Center