Add new interfaces/members to IReadOnlyObservableGroup

Author: Sergio0694

CommunityToolkit.Mvvm/Collections/IReadOnlyObservableGroup.cs

@@ -2,14 +2,16 @@
 // 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.Collections;
+using System.Collections.Specialized;
 using System.ComponentModel;
 
 namespace CommunityToolkit.Mvvm.Collections;
 
 /// <summary>
 /// An interface for a grouped collection of items.
 /// </summary>
-public interface IReadOnlyObservableGroup : INotifyPropertyChanged
+public interface IReadOnlyObservableGroup : INotifyPropertyChanged, INotifyCollectionChanged, IEnumerable
 {
     /// <summary>
     /// Gets the key for the current collection.
@@ -20,4 +22,12 @@ public interface IReadOnlyObservableGroup : INotifyPropertyChanged
     /// Gets the number of items currently in the grouped collection.
     /// </summary>
     int Count { get; }
+
+    /// <summary>
+    /// Gets the element at the specified index in the current collection.
+    /// </summary>
+    /// <param name="index">The zero-based index of the element to get.</param>
+    /// <returns>The element at the specified index in the read-only list.</returns>
+    /// <exception cref="System.ArgumentOutOfRangeException">Thrown if the index is out of range.</exception>
+    object? this[int index] { get; }
 }

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

@@ -71,4 +71,7 @@ public TKey Key
 
     /// <inheritdoc/>
     object IReadOnlyObservableGroup.Key => Key;
+
+    /// <inheritdoc/>
+    object? IReadOnlyObservableGroup.this[int index] => this[index];
 }

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

@@ -41,4 +41,7 @@ public ReadOnlyObservableGroup(ObservableGroup<TKey, TValue> group)
 
     /// <inheritdoc/>
     object IReadOnlyObservableGroup.Key => Key;
+
+    /// <inheritdoc/>
+    object? IReadOnlyObservableGroup.this[int index] => this[index];
 }