Merge pull request #4020 from MarchingCube/perf-inpc

Benchmark and simple optimization for INPC accessor.

src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs

@@ -1,7 +1,5 @@
 using System;
 using System.ComponentModel;
-using System.Linq;
-using System.Reactive.Linq;
 using System.Reflection;
 using Avalonia.Utilities;
 
@@ -31,7 +29,11 @@ namespace Avalonia.Data.Core.Plugins
             Contract.Requires<ArgumentNullException>(propertyName != null);
 
             reference.TryGetTarget(out object instance);
-            var p = instance.GetType().GetRuntimeProperties().FirstOrDefault(x => x.Name == propertyName);
+
+            const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Public |
+                                              BindingFlags.Static | BindingFlags.Instance;
+
+            var p = instance.GetType().GetProperty(propertyName, bindingFlags);
 
             if (p != null)
             {

tests/Avalonia.Benchmarks/Data/PropertyAccessorBenchmarks.cs

@@ -0,0 +1,57 @@
+using System;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using Avalonia.Data.Core.Plugins;
+using BenchmarkDotNet.Attributes;
+using JetBrains.Annotations;
+
+namespace Avalonia.Benchmarks.Data
+{
+    [MemoryDiagnoser, InProcess]
+    public class PropertyAccessorBenchmarks
+    {
+        private readonly InpcPropertyAccessorPlugin _plugin = new InpcPropertyAccessorPlugin();
+        private readonly TestObject _targetStrongRef = new TestObject();
+        private readonly WeakReference<object> _targetWeakRef;
+
+        public PropertyAccessorBenchmarks()
+        {
+            _targetWeakRef = new WeakReference<object>(_targetStrongRef);
+        }
+
+        [Benchmark]
+        public void InpcAccessor()
+        {
+            _plugin.Start(_targetWeakRef, nameof(TestObject.Test));
+        }
+
+        private class TestObject : INotifyPropertyChanged
+        {
+            private string _test;
+
+            public string Test
+            {
+                get => _test;
+                set
+                {
+                    if (_test == value)
+                    {
+                        return;
+                    }
+
+                    _test = value;
+
+                    OnPropertyChanged();
+                }
+            }
+
+            public event PropertyChangedEventHandler PropertyChanged;
+
+            [NotifyPropertyChangedInvocator]
+            protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+            {
+                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+            }
+        }
+    }
+}