From 35ee4f79762f933ca12ad27c9a3bb7201cc24dcd Mon Sep 17 00:00:00 2001
From: ahopper <alan@samsararesearch.com>
Date: Wed, 20 Nov 2019 11:04:20 +0000
Subject: [PATCH 1/3] Reduce calls to ToArray in PublishNext

---
 .../Reactive/LightweightObservableBase.cs     | 27 ++++++++++++++-----
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
index 41009e4cd3..b6c7cecfdc 100644
--- a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
+++ b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
@@ -111,25 +111,38 @@ namespace Avalonia.Reactive
 
         protected abstract void Initialize();
         protected abstract void Deinitialize();
-
+       
         protected void PublishNext(T value)
         {
             if (Volatile.Read(ref _observers) != null)
             {
-                IObserver<T>[] observers;
-
+                IObserver<T>[] observers = null;
+                IObserver<T> singleObserver = null;
                 lock (this)
                 {
                     if (_observers == null)
                     {
                         return;
                     }
-                    observers = _observers.ToArray();
+                    if (_observers.Count == 1)
+                    {
+                        singleObserver = _observers[0];
+                    }
+                    else
+                    {
+                        observers = _observers.ToArray();
+                    }
                 }
-
-                foreach (var observer in observers)
+                if (singleObserver != null)
                 {
-                    observer.OnNext(value);
+                    singleObserver.OnNext(value);
+                }
+                else
+                {
+                    foreach (var observer in observers)
+                    {
+                        observer.OnNext(value);
+                    }
                 }
             }
         }

From f7c644eb7567a865b95c3ba9dc95f9398d5969a7 Mon Sep 17 00:00:00 2001
From: ahopper <alan@samsararesearch.com>
Date: Wed, 20 Nov 2019 11:14:48 +0000
Subject: [PATCH 2/3] whitespace

---
 src/Avalonia.Base/Reactive/LightweightObservableBase.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
index b6c7cecfdc..f5052e5858 100644
--- a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
+++ b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
@@ -111,7 +111,7 @@ namespace Avalonia.Reactive
 
         protected abstract void Initialize();
         protected abstract void Deinitialize();
-       
+
         protected void PublishNext(T value)
         {
             if (Volatile.Read(ref _observers) != null)

From 8879d4c92d97dac93b9e659950f47f87da005c9e Mon Sep 17 00:00:00 2001
From: ahopper <alan@samsararesearch.com>
Date: Wed, 20 Nov 2019 16:12:09 +0000
Subject: [PATCH 3/3] added benchmark

---
 .../Data/BindingsBenchmark.cs                    | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs b/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
index d1ca77c980..a320f07063 100644
--- a/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
+++ b/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
@@ -19,6 +19,22 @@ namespace Avalonia.Benchmarks.Data
             instance.Bind(TestClass.IntValueProperty, binding);
         }
 
+        [Benchmark]
+        public void UpdateTwoWayBinding_Via_Binding()
+        {
+            var instance = new TestClass();
+
+            var binding = new Binding(nameof(TestClass.BoundValue), BindingMode.TwoWay)
+            {
+                Source = instance
+            };
+
+            instance.Bind(TestClass.IntValueProperty, binding);
+            for (int i = 0; i < 60; i++)
+            {
+                instance.IntValue = i;
+            }
+        }
         private class TestClass : AvaloniaObject
         {
             public static readonly StyledProperty<int> IntValueProperty =