We have the following scenario:

• a dialog that contains a TreeView
• the TreeView is not expanded, when the dialog is opened, only the root node is displayed
• the children are loaded on demand, when the parent node is expanded
• there is a public async Task LoadChildrenAsync() that loads the children from the source
• the loading operation might take a few seconds

The problem is when you close the dialog before the loading is finished, a NullReferenceException occurs.

System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Blazor.Components.Common.Trees.TelerikTreeDataSource.GetTreeItems(IEnumerable`1 data, Int32 level, String parentIndex)