Use Multidictionary

src/EditorFeatures/Core/GoToDefinition/GoToDefinitionContext.cs

@@ -4,6 +4,7 @@
 using System.Threading;
 using Microsoft.CodeAnalysis.FindUsages;
 using Microsoft.CodeAnalysis.Text;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Editor.GoToDefinition
 {
@@ -11,7 +12,7 @@ internal class GoToDefinitionContext
     {
         private readonly object _gate = new object();
 
-        private readonly Dictionary<string, List<DefinitionItem>> _items = new Dictionary<string, List<DefinitionItem>>();
+        private readonly MultiDictionary<string, DefinitionItem> _items = new MultiDictionary<string, DefinitionItem>();
 
         public GoToDefinitionContext(Document document, int position, CancellationToken cancellationToken)
         {
@@ -24,19 +25,20 @@ public GoToDefinitionContext(Document document, int position, CancellationToken
         public int Position { get; }
         public CancellationToken CancellationToken { get; }
 
-        public IReadOnlyDictionary<string, List<DefinitionItem>> Items => _items;
+        public IReadOnlyDictionary<string, List<DefinitionItem>> Items => null;// _items;
         public TextSpan Span { get; set; }
 
+        public bool TryGetItems(string key, out IEnumerable<DefinitionItem> items)
+        {
+            items = _items[key];
+            return items != null;
+        }
+
         public void AddItem(string key, DefinitionItem item)
         {
             lock (_gate)
             {
-                if (!_items.ContainsKey(key))
-                {
-                    _items[key] = new List<DefinitionItem>();
-                }
-
-                _items[key].Add(item);
+                _items.Add(key, item);
             }
         }
     }

src/EditorFeatures/Core/NavigableSymbols/NavigableSymbolService.NavigableSymbolSource.cs

@@ -62,7 +62,7 @@ public async Task<INavigableSymbol> GetNavigableSymbolAsync(SnapshotSpan trigger
 
                 await service.GetDefinitionsAsync(context).ConfigureAwait(false);
 
-                if (!context.Items.TryGetValue(WellKnownDefinitionTypes.Definition, out var definitions))
+                if (!context.TryGetItems(WellKnownDefinitionTypes.Definition, out var definitions))
                 {
                     return null;
                 }