remove need for seperate NotificationManager class.

samples/ControlCatalog/ViewModels/MainWindowViewModel.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Text;
 using System.Threading.Tasks;
+using Avalonia;
 using Avalonia.Controls.Notifications;
 using Avalonia.Threading;
 
@@ -15,19 +16,20 @@ namespace ControlCatalog.ViewModels
             {
                 await Task.Delay(5000);
 
-                NotificationManager.Instance.Show(new NotificationViewModel { Title = "Warning", Message = "Please save your work before closing." }, "Main");
+                
+                Application.Current.MainWindow.LocalNotificationManager.Show(new NotificationViewModel { Title = "Warning", Message = "Please save your work before closing." });
 
                 await Task.Delay(1500);
-                NotificationManager.Instance.Show(new NotificationContent { Message = "Test2", Type = NotificationType.Error }, "Main");
+                Application.Current.MainWindow.LocalNotificationManager.Show(new NotificationContent { Message = "Test2", Type = NotificationType.Error });
 
                 await Task.Delay(2000);
-                NotificationManager.Instance.Show(new NotificationContent { Message = "Test3", Type = NotificationType.Warning }, "Main");
+                Application.Current.MainWindow.LocalNotificationManager.Show(new NotificationContent { Message = "Test3", Type = NotificationType.Warning });
 
                 await Task.Delay(2500);
-                NotificationManager.Instance.Show(new NotificationContent { Message = "Test4", Type = NotificationType.Success }, "Main");
+                Application.Current.MainWindow.LocalNotificationManager.Show(new NotificationContent { Message = "Test4", Type = NotificationType.Success });
 
                 await Task.Delay(500);
-                NotificationManager.Instance.Show("Test5", "Main");
+                Application.Current.MainWindow.LocalNotificationManager.Show("Test5");
 
             });
         }

samples/ControlCatalog/ViewModels/NotificationViewModel.cs

@@ -1,4 +1,5 @@
 using System.Reactive;
+using Avalonia;
 using Avalonia.Controls.Notifications;
 using ReactiveUI;
 
@@ -10,7 +11,7 @@ namespace ControlCatalog.ViewModels
         {
             OKCommand = ReactiveCommand.Create(() =>
             {
-                NotificationManager.Instance.Show("Notification Accepted", "Main");
+                Application.Current.MainWindow.LocalNotificationManager.Show("Notification Accepted");
             });
         }
 

src/Avalonia.Controls/Notifications/INotificationManager.cs

@@ -4,6 +4,6 @@ namespace Avalonia.Controls.Notifications
 {
     public interface INotificationManager
     {
-        void Show(object content, string areaName = "", TimeSpan? expirationTime = null, Action onClick = null, Action onClose = null);
+        void Show(object content, TimeSpan? expirationTime = null, Action onClick = null, Action onClose = null);
     }
 }

src/Avalonia.Controls/Notifications/NotificationArea.cs

@@ -7,7 +7,7 @@ using Avalonia.Interactivity;
 
 namespace Avalonia.Controls.Notifications
 {
-    public class NotificationArea : TemplatedControl
+    public class NotificationArea : TemplatedControl, INotificationManager
     {
         private IList _items;
 
@@ -31,7 +31,6 @@ namespace Avalonia.Controls.Notifications
 
         public NotificationArea()
         {
-            NotificationManager.AddArea(this);
         }
 
         static NotificationArea()
@@ -50,7 +49,7 @@ namespace Avalonia.Controls.Notifications
             _items = itemsControl?.Children;
         }
 
-        public async void Show(object content, TimeSpan expirationTime, Action onClick, Action onClose)
+        public async void Show(object content, TimeSpan? expirationTime, Action onClick, Action onClose)
         {
             var notification = new Notification
             {
@@ -82,7 +81,8 @@ namespace Avalonia.Controls.Notifications
             {
                 return;
             }
-            await Task.Delay(expirationTime);
+
+            await Task.Delay(expirationTime ?? TimeSpan.FromSeconds(5));
 
             notification.Close();
         }

src/Avalonia.Controls/Notifications/NotificationManager.cs

@@ -1,53 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Threading;
-
-namespace Avalonia.Controls.Notifications
-{
-    public class NotificationManager : INotificationManager
-    {
-        private static readonly List<NotificationArea> Areas = new List<NotificationArea>();
-        private static Window _window;
-
-        public static NotificationManager Instance = new NotificationManager();
-
-        public void Show(object content, string areaName = "", TimeSpan? expirationTime = null, Action onClick = null,
-            Action onClose = null)
-        {
-            if (!Dispatcher.UIThread.CheckAccess())
-            {
-                Dispatcher.UIThread.Post(
-                    new Action(() => Show(content, areaName, expirationTime, onClick, onClose)));
-                return;
-            }
-
-            if (expirationTime == null)
-                expirationTime = TimeSpan.FromSeconds(5);
-
-            if (areaName == string.Empty && _window == null)
-            {
-                var workArea = Application.Current.MainWindow.Screens.Primary.WorkingArea;
-
-                _window = new Window
-                {
-                    Position = workArea.Position,
-                    Width = workArea.Width,
-                    Height = workArea.Height
-                };
-
-                _window.Show();
-            }
-
-            foreach (var area in Areas.Where(a => a.Name == areaName))
-            {
-                area.Show(content, (TimeSpan)expirationTime, onClick, onClose);
-            }
-        }
-
-        internal static void AddArea(NotificationArea area)
-        {
-            Areas.Add(area);
-        }
-    }
-}

src/Avalonia.Controls/TopLevel.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Linq;
 using System.Reactive.Linq;
 using Avalonia.Controls.Notifications;
 using Avalonia.Controls.Primitives;
@@ -103,7 +104,7 @@ namespace Avalonia.Controls
 
             PlatformImpl = impl;
 
-            LocalNotificationManager = new NotificationManager();
+            LocalNotificationManager = new NotificationArea();
 
             dependencyResolver = dependencyResolver ?? AvaloniaLocator.Current;
             var styler = TryGetService<IStyler>(dependencyResolver);
@@ -414,5 +415,20 @@ namespace Avalonia.Controls
         {
             (this as IInputRoot).MouseDevice.SceneInvalidated(this, e.DirtyRect);
         }
+
+        protected override void OnTemplateApplied(TemplateAppliedEventArgs e)
+        {
+            var adornerLayer = this.GetVisualDescendants()
+                .OfType<AdornerDecorator>()
+                .FirstOrDefault()
+                ?.AdornerLayer;
+
+            if (adornerLayer != null)
+            {
+                adornerLayer.Children.Add(LocalNotificationManager as IControl);
+            }
+
+            base.OnTemplateApplied(e);
+        }
     }
 }