Sample improves

* No remove axaml files for makes the sample simpler.
* Creation of utilities class.
* Avoid using ref Bitmap on MainViewModel.
* Avoid application crashing when dotnet.png or avalonia.png are missing. Using an replace embeded image instead.
* Conditionally invoke of UseAvaloniaNative at runtime.

src/Controls/ViewModels/MainViewModel.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Runtime.CompilerServices;
 
 using Avalonia.Media.Imaging;
 
@@ -13,22 +12,23 @@ namespace AvaloniaCoreRTDemo.Controls.ViewModels
         private readonly IBitmap _dotNetImage;
         private readonly IBitmap _avaloniaImage;
 
-        public IBitmap DotNetImage
-        {
-            get { return _dotNetImage; }
-            set { this.RaiseAndSetIfChanged(ref Unsafe.AsRef(this._dotNetImage), value); }
-        }
+        public IBitmap DotNetImage => this._dotNetImage;
 
-        public IBitmap AvaloniaImage
-        {
-            get { return _avaloniaImage; }
-            set { this.RaiseAndSetIfChanged(ref Unsafe.AsRef(this._avaloniaImage), value); }
-        }
+        public IBitmap AvaloniaImage => this._avaloniaImage;
 
         public MainViewModel()
         {
-            this._dotNetImage = new Bitmap(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "dotnet.png"));
-            this._avaloniaImage = new Bitmap(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "avalonia.png"));
+            this._dotNetImage = Utilities.GetImageFromFile(GetImageFullPath("dotnet.png"));
+            this._avaloniaImage = Utilities.GetImageFromFile(GetImageFullPath("avalonia.png"));
+        }
+
+        private static String GetImageFullPath(String fileName)
+            => Path.Combine(AppDomain.CurrentDomain.BaseDirectory, fileName);
+
+        ~MainViewModel()
+        {
+            this._dotNetImage.Dispose();
+            this._avaloniaImage.Dispose();
         }
     }
 }