add implementation of url event for application class.

src/Avalonia.Controls/Application.cs

@@ -55,6 +55,8 @@ namespace Avalonia
         /// <inheritdoc/>
         public event EventHandler<ResourcesChangedEventArgs> ResourcesChanged;
 
+        public event EventHandler<UrlOpenedEventArgs> UrlOpened; 
+
         /// <summary>
         /// Creates an instance of the <see cref="Application"/> class.
         /// </summary>
@@ -247,7 +249,17 @@ namespace Avalonia
 
         public virtual void OnFrameworkInitializationCompleted()
         {
-            
+            var applicationPlatform = AvaloniaLocator.Current.GetService<IApplicationPlatform>();
+
+            if (applicationPlatform != null)
+            {
+                applicationPlatform.FilesOpened = OnFilesOpened;
+            }
+        }
+
+        private void OnFilesOpened(string[] urls)
+        {
+            UrlOpened?.Invoke(this, new UrlOpenedEventArgs (urls));
         }
 
         private void NotifyResourcesChanged(ResourcesChangedEventArgs e)

src/Avalonia.Controls/Platform/IApplicationPlatform.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Avalonia.Platform
+{
+    public interface IApplicationPlatform
+    {
+        Action<string[]> FilesOpened { get; set; }
+    }
+}

src/Avalonia.Controls/UrlOpenedEventArgs.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace Avalonia
+{
+    public class UrlOpenedEventArgs : EventArgs
+    {
+        public UrlOpenedEventArgs(string[] urls)
+        {
+            Urls = urls;
+        }
+        
+        public string[] Urls { get; }
+    }
+}

src/Avalonia.Native/AvaloniaNativeApplicationPlatform.cs

@@ -0,0 +1,16 @@
+using System;
+using Avalonia.Native.Interop;
+using Avalonia.Platform;
+
+namespace Avalonia.Native
+{
+    internal class AvaloniaNativeApplicationPlatform : CallbackBase, IApplicationPlatform, IAvnApplicationEvents
+    {
+        public Action<string[]> FilesOpened { get; set; }
+        
+        void IAvnApplicationEvents.FilesOpened(IAvnStringArray urls)
+        {
+            FilesOpened?.Invoke(urls.ToStringArray());
+        }
+    }
+}

src/Avalonia.Native/AvaloniaNativePlatform.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Runtime.InteropServices;
-using System.Security.Cryptography;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
@@ -9,7 +8,6 @@ using Avalonia.Native.Interop;
 using Avalonia.OpenGL;
 using Avalonia.Platform;
 using Avalonia.Rendering;
-using Avalonia.Platform.Interop;
 
 namespace Avalonia.Native
 {
@@ -86,7 +84,10 @@ namespace Avalonia.Native
         void DoInitialize(AvaloniaNativePlatformOptions options)
         {
             _options = options;
-            _factory.Initialize(new GCHandleDeallocator());
+            
+            var applicationPlatform = new AvaloniaNativeApplicationPlatform();
+            
+            _factory.Initialize(new GCHandleDeallocator(), applicationPlatform);
             if (_factory.MacOptions != null)
             {
                 var macOpts = AvaloniaLocator.Current.GetService<MacOSPlatformOptions>();
@@ -97,6 +98,7 @@ namespace Avalonia.Native
             }
 
             AvaloniaLocator.CurrentMutable
+                .Bind<IApplicationPlatform>().ToConstant(applicationPlatform)
                 .Bind<IPlatformThreadingInterface>()
                 .ToConstant(new PlatformThreadingInterface(_factory.CreatePlatformThreadingInterface()))
                 .Bind<ICursorFactory>().ToConstant(new CursorFactory(_factory.CreateCursorFactory()))