Merge pull request #60 from xamarin/warnings-WP8-4014

Turn off suppression of warning CS4014
Port TaskExtensions from WinRT projects to WP8
Update implementation of OpenUriAction to use TaskExtensions

Xamarin.Forms.Platform.WP8/TaskExtensions.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Windows.Foundation;
+
+namespace Xamarin.Forms
+{
+	internal static class TaskExtensions
+	{
+		public static void WatchForError(this IAsyncAction self)
+		{
+			self.AsTask().WatchForError();
+		}
+
+		public static void WatchForError<T>(this IAsyncOperation<T> self)
+		{
+			self.AsTask().WatchForError();
+		}
+
+		public static void WatchForError(this Task self)
+		{
+			SynchronizationContext context = SynchronizationContext.Current;
+			if (context == null)
+				return;
+
+			self.ContinueWith(t => {
+				                       Exception exception = t.Exception.InnerExceptions.Count > 1 ? t.Exception : t.Exception.InnerException;
+
+				                       context.Post(e => { throw (Exception)e; }, exception);
+			}, CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, TaskScheduler.Default);
+		}
+	}
+}

Xamarin.Forms.Platform.WP8/WP8PlatformServices.cs

@@ -134,7 +134,7 @@ namespace Xamarin.Forms
 
 		public void OpenUriAction(Uri uri)
 		{
-			Launcher.LaunchUriAsync(uri);
+			Launcher.LaunchUriAsync(uri).WatchForError();
 		}
 
 		public void StartTimer(TimeSpan interval, Func<bool> callback)

Xamarin.Forms.Platform.WP8/Xamarin.Forms.Platform.WP8.csproj

@@ -32,7 +32,7 @@
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-    <NoWarn>4014;0618;0219</NoWarn>
+    <NoWarn>0618;0219</NoWarn>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -202,6 +202,7 @@
       <DependentUpon>TableView.xaml</DependentUpon>
     </Compile>
     <Compile Include="TableViewRenderer.cs" />
+    <Compile Include="TaskExtensions.cs" />
     <Compile Include="TextAlignmentToHorizontalAlignmentConverter.cs" />
     <Compile Include="TextCellRenderer.cs" />
     <Compile Include="TimePickerRenderer.cs" />