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] 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);
+                    }
                 }
             }
         }