Hello SWAYAM KAR,
Thank you for the screens and the clarification.
Do you mean that you are creating the TreeViewItems in code and then building the hierarchy yourself?
If this is the case then this may be the reason for the strange behavior.
UI Virtualization means that the TreeView will create UI containers (TreeViewItems) only for the visible items and it will reuse these containers when needed.
If you create the TreeViewItems yourself then a large number of items will already be created and there is little that can be done to improve the performance.
In this case I can suggest databinding the TreeView and using an <Image /> in the data template instead of a setting the DefaultImageSrc.
Would this be an option for you?
the Telerik team
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