This was done to prevent the case where the user collapses the node before it's fully expanded and the ClientNodeExpand is never fired. This could cause problems in some scenarios, but you are right that some scenarios (especially those that rely on checking the height of the TreeView/Node) require an event that is fired after the Node is fully expanded/collapsed. That's why we are planning to add something like AnimationEnd event so we can cover both scenarios without breaking existing functionality.
Interestingly, using a timeout set to the duration of the animation should work as a workaround. What was the problem you encountered in this case?
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