Improve caching of KeyChangedEventArgs

Author: Sergio0694

CommunityToolkit.Mvvm/Collections/Internals/ObservableGroupHelper.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace CommunityToolkit.Mvvm.Collections.Internals;
+
+/// <summary>
+/// A helper type for the <see cref="ObservableGroup{TKey, TValue}"/> type.
+/// </summary>
+internal static class ObservableGroupHelper
+{
+    /// <summary>
+    /// The cached <see cref="PropertyChangedEventArgs"/> for <see cref="IReadOnlyObservableGroup.Key"/>
+    /// </summary>
+    public static readonly PropertyChangedEventArgs KeyChangedEventArgs = new(nameof(IReadOnlyObservableGroup.Key));
+}

CommunityToolkit.Mvvm/Collections/ObservableGroup{TKey,TValue}.cs

@@ -4,9 +4,9 @@
 
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.ComponentModel;
 using System.Diagnostics;
 using System.Linq;
+using CommunityToolkit.Mvvm.Collections.Internals;
 
 namespace CommunityToolkit.Mvvm.Collections;
 
@@ -20,11 +20,6 @@ namespace CommunityToolkit.Mvvm.Collections;
 public class ObservableGroup<TKey, TValue> : ObservableCollection<TValue>, IGrouping<TKey, TValue>, IReadOnlyObservableGroup<TKey>
     where TKey : notnull
 {
-    /// <summary>
-    /// The cached <see cref="PropertyChangedEventArgs"/> for <see cref="Key"/>
-    /// </summary>
-    private static readonly PropertyChangedEventArgs KeyChangedEventArgs = new(nameof(Key));
-
     /// <summary>
     /// Initializes a new instance of the <see cref="ObservableGroup{TKey, TValue}"/> class.
     /// </summary>
@@ -69,7 +64,7 @@ public TKey Key
             {
                 this.key = value;
 
-                OnPropertyChanged(KeyChangedEventArgs);
+                OnPropertyChanged(ObservableGroupHelper.KeyChangedEventArgs);
             }
         }
     }