Added tests for stream binding operator in XAML.

samples/BindingTest/BindingTest.csproj

@@ -60,6 +60,10 @@
       <HintPath>..\..\packages\System.Reactive.Interfaces.3.0.0\lib\net45\System.Reactive.Interfaces.dll</HintPath>
       <Private>True</Private>
     </Reference>
+    <Reference Include="System.Reactive.Linq, Version=3.0.0.0, Culture=neutral, PublicKeyToken=94bc3704cddfc263, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\System.Reactive.Linq.3.0.0\lib\net45\System.Reactive.Linq.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
     <Reference Include="System.Xml.Linq" />
     <Reference Include="System.Data.DataSetExtensions" />
     <Reference Include="Microsoft.CSharp" />

samples/BindingTest/MainWindow.xaml

@@ -44,6 +44,8 @@
           <StackPanel Margin="18" Gap="4" Width="200" HorizontalAlignment="Left">
             <TextBlock FontSize="16" Text="Scheduler"/>
             <TextBox Watermark="Background Thread" Text="{Binding CurrentTime, Mode=OneWay}"/>
+            <TextBlock FontSize="16" Text="Stream Operator"/>
+            <TextBox Watermark="StreamOperator" Text="{Binding CurrentTimeObservable^, Mode=OneWay}"/>
           </StackPanel>
         </StackPanel>
       </StackPanel>

samples/BindingTest/ViewModels/MainWindowViewModel.cs

@@ -49,6 +49,9 @@ namespace BindingTest.ViewModels
                     Thread.Sleep(1000);
                 }
             });
+
+            CurrentTimeObservable = Observable.Timer(TimeSpan.Zero, TimeSpan.FromSeconds(1))
+                .Select(x => DateTimeOffset.Now.ToString());
         }
 
         public ObservableCollection<TestItem> Items { get; }
@@ -85,6 +88,7 @@ namespace BindingTest.ViewModels
             private set { this.RaiseAndSetIfChanged(ref _currentTime, value); }
         }
 
+        public IObservable<string> CurrentTimeObservable { get; }
         public ReactiveCommand<object> StringValueCommand { get; }
 
         public DataAnnotationsErrorViewModel DataAnnotationsValidation { get; } = new DataAnnotationsErrorViewModel();

samples/BindingTest/packages.config

@@ -4,4 +4,5 @@
   <package id="Splat" version="1.6.2" targetFramework="net46" />
   <package id="System.Reactive.Core" version="3.0.0" targetFramework="net45" />
   <package id="System.Reactive.Interfaces" version="3.0.0" targetFramework="net45" />
+  <package id="System.Reactive.Linq" version="3.0.0" targetFramework="net45" />
 </packages>

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests.cs

@@ -1,6 +1,7 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using System.Reactive.Subjects;
 using Avalonia.Controls;
 using Avalonia.UnitTests;
 using Xunit;
@@ -193,5 +194,29 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 Assert.Equal("foo", textBlock.Text);
             }
         }
+
+        [Fact]
+        public void Stream_Binding_To_Observable_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.MockWindowingPlatform))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <TextBlock Name='textblock' Text='{Binding Observable^}'/>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var textBlock = (TextBlock)window.Content;
+                var observable = new BehaviorSubject<string>("foo");
+
+                window.DataContext = new { Observable = observable };
+                window.ApplyTemplate();
+
+                Assert.Equal("foo", textBlock.Text);
+                observable.OnNext("bar");
+                Assert.Equal("bar", textBlock.Text);
+            }
+        }
     }
 }