[UWP] Escape key returns ActionSheet result (#208)

When awaiting a DisplayActionSheet in UWP, pressing the escape key with
the ActionSheet open would dismiss the dialog but not return a result.

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40998.cs

@@ -0,0 +1,41 @@
+using System;
+
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 40998, "[UWP] Pressing escape with an awaited DisplayActionSheet doesn't return a result", PlatformAffected.WinRT)]
+	public class Bugzilla40998 : TestContentPage
+	{
+		protected override void Init()
+		{
+			var resultLabel = new Label
+			{
+				Text = "ActionSheet Result - use the ActionSheet to show the result"
+			};
+			Content = new StackLayout
+			{
+				Children =
+				{
+					resultLabel,
+					new Button
+					{
+						Text = "Click to display ActionSheet",
+						Command = new Command(async () =>
+						{
+							var result = await DisplayActionSheet("Test ActionSheet", "Cancel", "Destroy", new string[] { "Test Button" });
+							resultLabel.Text = result;
+						})
+					}
+				}
+			};
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -105,6 +105,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40333.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla31806.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41078.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40998.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34727.cs" />

Xamarin.Forms.Platform.WinRT/Platform.cs

@@ -13,7 +13,9 @@ using Windows.UI.Xaml.Media;
 using Windows.UI.Xaml.Media.Animation;
 
 #if WINDOWS_UWP
+using Windows.Foundation;
 using Windows.Foundation.Metadata;
+using Windows.UI.Core;
 using Windows.UI.ViewManagement;
 #endif
 
@@ -591,6 +593,17 @@ namespace Xamarin.Forms.Platform.WinRT
 				options.SetResult((string)e.ClickedItem);
 			};
 
+			TypedEventHandler<CoreWindow, CharacterReceivedEventArgs> onEscapeButtonPressed = delegate(CoreWindow window, CharacterReceivedEventArgs args)
+			{
+				if (args.KeyCode == 27)
+				{
+					dialog.Hide();
+					options.SetResult(ContentDialogResult.None.ToString());
+				}
+			};
+
+			Window.Current.CoreWindow.CharacterReceived += onEscapeButtonPressed;
+
 			_actionSheetOptions = options;
 
 			if (options.Cancel != null)
@@ -604,6 +617,8 @@ namespace Xamarin.Forms.Platform.WinRT
 				options.SetResult(options.Cancel);
 			else if (result == ContentDialogResult.Primary)
 				options.SetResult(options.Destruction);
+
+			Window.Current.CoreWindow.CharacterReceived -= onEscapeButtonPressed;
 		}
 #else
 		void OnPageActionSheet(Page sender, ActionSheetArguments options)