Add index to OrderedDictionary debugger display

src/libraries/Common/tests/System/Collections/DebugView.Tests.cs

@@ -21,6 +21,7 @@ private static IEnumerable<object[]> TestDebuggerAttributes_GenericDictionaries(
             yield return new object[] { new ReadOnlyDictionary<int, string>(new Dictionary<int, string>()), new KeyValuePair<string, string>[0] };
             yield return new object[] { new SortedDictionary<string, int>(), new KeyValuePair<string, string>[0] };
             yield return new object[] { new SortedList<int, string>(), new KeyValuePair<string, string>[0] };
+            yield return new object[] { new OrderedDictionary<int, string>(), new KeyValuePair<string, string>[0] };
 
             yield return new object[] { new Dictionary<int, string>{{1, "One"}, {2, "Two"}},
                 new KeyValuePair<string, string>[]
@@ -69,6 +70,14 @@ private static IEnumerable<object[]> TestDebuggerAttributes_GenericDictionaries(
                     new ("[2]", "\"Two\""),
                 }
             };
+
+            yield return new object[] { new OrderedDictionary<int, string>{{1, "One"}, {2, "Two"}},
+                new KeyValuePair<string, string>[]
+                {
+                    new ("[0/1]", "\"One\""),
+                    new ("[1/2]", "\"Two\""),
+                }
+            };
         }
 
         private static IEnumerable<object[]> TestDebuggerAttributes_AdditionalGenericDictionaries()

src/libraries/System.Collections/src/System.Collections.csproj

@@ -17,6 +17,7 @@
     <Compile Include="$(CoreLibSharedDir)System\Collections\ObjectModel\CollectionHelpers.cs" Link="Common\System\Collections\ObjectModel\CollectionHelpers.cs" />
     <Compile Include="System\Collections\Generic\LinkedList.cs" />
     <Compile Include="System\Collections\Generic\OrderedDictionary.cs" />
+    <Compile Include="System\Collections\Generic\OrderedDictionaryDebugView.cs" />
     <Compile Include="System\Collections\Generic\PriorityQueue.cs" />
     <Compile Include="System\Collections\Generic\PriorityQueueDebugView.cs" />
     <Compile Include="System\Collections\Generic\SortedDictionary.cs" />

src/libraries/System.Collections/src/System/Collections/Generic/OrderedDictionary.cs

@@ -23,7 +23,7 @@
     /// Operations on the collection have algorithmic complexities that are similar to that of the <see cref="List{T}"/>
     /// class, except with lookups by key similar in complexity to that of <see cref="Dictionary{TKey, TValue}"/>.
     /// </remarks>
-    [DebuggerTypeProxy(typeof(IDictionaryDebugView<,>))]
+    [DebuggerTypeProxy(typeof(OrderedDictionaryDebugView<,>))]
     [DebuggerDisplay("Count = {Count}")]
 #if SYSTEM_COLLECTIONS
     public

src/libraries/System.Collections/src/System/Collections/Generic/OrderedDictionaryDebugView.cs

@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+
+namespace System.Collections.Generic
+{
+    internal sealed class OrderedDictionaryDebugView<TKey, TValue> where TKey : notnull
+    {
+        private readonly OrderedDictionary<TKey, TValue> _dictionary;
+
+        public OrderedDictionaryDebugView(OrderedDictionary<TKey, TValue> dictionary)
+        {
+            ArgumentNullException.ThrowIfNull(dictionary);
+            _dictionary = dictionary;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public DebugViewOrderedDictionaryItem<TKey, TValue>[] Items
+        {
+            get
+            {
+                var items = new DebugViewOrderedDictionaryItem<TKey, TValue>[_dictionary.Count];
+                int index = 0;
+                foreach (KeyValuePair<TKey, TValue> kvp in _dictionary)
+                {
+                    items[index] = new DebugViewOrderedDictionaryItem<TKey, TValue>(index, kvp.Key, kvp.Value);
+                    index++;
+                }
+                return items;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Defines an index/key/value triple for displaying an item of an ordered dictionary by a debugger.
+    /// </summary>
+    [DebuggerDisplay("{Value}", Name = "[{Index}/{Key}]")]
+    internal readonly struct DebugViewOrderedDictionaryItem<TKey, TValue>
+    {
+        public DebugViewOrderedDictionaryItem(int index, TKey key, TValue value)
+        {
+            Index = index;
+            Key = key;
+            Value = value;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public int Index { get; }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.Collapsed)]
+        public TKey Key { get; }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.Collapsed)]
+        public TValue Value { get; }
+    }
+}