The provided project is greatly appreciated. When I unzip the folder and open the project, I just want to mention it is actually.NET9 project, not.NET8. However, both versions are compatible, and you can use whatever you want. I was able to examine the TestRadTreeView and notice that there are extremely large values set to some of RadTreeView's properties that would likely make the interface unusable. For example, there were the following properties set in the Designer.cs that are not ok:
Their values may vary, but very big deviations may make the nodes too big or too far from one another, which does not look good.
I attached a project where RadTreeView is added at design time on the form and it is serialized with its default values. Then I populate the tree using your approach and the nodes now appear normally in the RadTreeView. Can you give the provided project a try and see how it works?
Regards,
Nadya | Tech Support Engineer
Progress Telerik