Different VisualItem depends on DataBoundItem

        public RadForm1()
        {
            InitializeComponent();
            InitializeViewAppearance();
            this.radListControl1.ItemHeight = 40;
        }
        private void InitializeViewAppearance()
        {
            var notifications = new List<Notification> {
                 new NotificationA {Name = "Foo"},
                 new NotificationA {Name = "Bar"},
                 new NotificationB { Degree = 180 }
             };
            for (var i = 0; i < 100000; i++)
            {
                notifications.Add(new NotificationA { Name = $"test item {i}" });
            }
            radListControl1.CreatingVisualListItem += OnNotificationItemCreating;
            radListControl1.DataSource = notifications;
        }
        private void OnNotificationItemCreating(object sender, CreatingVisualListItemEventArgs args)
        {
            args.VisualItem = new NotificationVisualItem();
        }

        public class NotificationVisualItem : RadListVisualItem
        {
            private LightVisualElement notificationATitleElement;
            private LightVisualElement notificationBTitleElement;
            private StackLayoutPanel stackLayout;

            protected override void CreateChildElements()
            {
                base.CreateChildElements();

                stackLayout = new StackLayoutPanel();
                stackLayout.Orientation = System.Windows.Forms.Orientation.Vertical;

                notificationATitleElement = new LightVisualElement();
                notificationATitleElement.TextAlignment = ContentAlignment.MiddleLeft;
                notificationATitleElement.Margin = new Padding(10);
                notificationATitleElement.ForeColor = Color.Red;

                notificationBTitleElement = new LightVisualElement();
                notificationBTitleElement.TextAlignment = ContentAlignment.MiddleLeft;
                notificationBTitleElement.Margin = new Padding(10);
                notificationBTitleElement.ForeColor = Color.Blue;

                stackLayout.Children.Add(notificationATitleElement);
                stackLayout.Children.Add(notificationBTitleElement); 

                Padding = new Padding(5);
                Shape = new RoundRectShape(3);
                BorderColor = Color.FromArgb(255, 110, 153, 210);
                BorderGradientStyle = GradientStyles.Solid;
                DrawBorder = true;
                DrawFill = true;
                BackColor = Color.FromArgb(255, 230, 238, 254);
                GradientStyle = GradientStyles.Solid;

                this.Children.Add(stackLayout);
            }

            public override void Synchronize()
            {
                base.Synchronize();
                this.DrawText = false;
                NotificationA dataItemA = this.Data.DataBoundItem as NotificationA;
                NotificationB dataItemB = this.Data.DataBoundItem as NotificationB;
                if (dataItemA != null)
                {
                    notificationATitleElement.Visibility = ElementVisibility.Visible;
                    notificationBTitleElement.Visibility = ElementVisibility.Collapsed;
                    notificationATitleElement.Text = dataItemA.Name;
                }
                else if (dataItemB != null)
                {
                    notificationATitleElement.Visibility = ElementVisibility.Collapsed;
                    notificationBTitleElement.Visibility = ElementVisibility.Visible;
                    notificationBTitleElement.Text = dataItemB.Degree.ToString(); ;
                }
            }
        } 

        internal class Notification
        {
            public int Id { get; set; }
        }
        internal class NotificationA : Notification
        {
            public string Name { get; set; }
            public string Type => nameof(NotificationA);
        }

        internal class NotificationB : Notification
        {
            public int Degree { get; set; }
            public string Type => nameof(NotificationB);
        }