To reproduces: add a RadTreeView and set up Object-relational hierarchy. Use the following code: NorthwindEntities context = new NorthwindEntities(); public Form1() { InitializeComponent(); context.Categories.Load(); context.Products.Load(); this.radTreeView1.DataSource = context.Categories.Local.ToBindingList(); this.radTreeView1.DisplayMember = "CategoryName\\ProductName"; this.radTreeView1.ChildMember = "Categories\\Products"; } private void radButton1_Click(object sender, EventArgs e) { this.radTreeView1.ChildMember = "Products\\Categories"; this.radTreeView1.DisplayMember = "ProductName\\CategoryName"; this.radTreeView1.DataSource = context.Products.Local.ToBindingList(); } When you click the RadButton, NullReferenceException occurs. Resolution: Add more descriptive exception message.