Make menu handler lists readonly

Author: shana

src/GitHub.Exports/Services/IMenuProvider.cs

@@ -12,11 +12,11 @@ public interface IMenuProvider
         /// <summary>
         /// Registered via AddTopLevelMenuItem
         /// </summary>
-        IEnumerable<IMenuHandler> Menus { get; set; }
+        IReadOnlyCollection<IMenuHandler> Menus { get; }
 
         /// <summary>
         /// Registered via AddDynamicMenuItem
         /// </summary>
-        IEnumerable<IDynamicMenuHandler> DynamicMenus { get; set; }
+        IReadOnlyCollection<IDynamicMenuHandler> DynamicMenus { get; }
     }
 }

src/GitHub.VisualStudio/Menus/MenuProvider.cs

@@ -1,16 +1,23 @@
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.ComponentModel.Composition;
+using System.Linq;
 
 namespace GitHub.VisualStudio.Menus
 {
     [Export(typeof(IMenuProvider))]
     [PartCreationPolicy(CreationPolicy.Shared)]
     public class MenuProvider : IMenuProvider
     {
-        [ImportMany]
-        public IEnumerable<IMenuHandler> Menus { get; set; }
+        public IReadOnlyCollection<IMenuHandler> Menus { get; private set; }
 
-        [ImportMany]
-        public IEnumerable<IDynamicMenuHandler> DynamicMenus { get; set; }
+        public IReadOnlyCollection<IDynamicMenuHandler> DynamicMenus { get; private set; }
+
+        [ImportingConstructor]
+        public MenuProvider([ImportMany] IEnumerable<IMenuHandler> menus, [ImportMany] IEnumerable<IDynamicMenuHandler> dynamicMenus)
+        {
+            Menus = new ReadOnlyCollection<IMenuHandler>(menus.ToList());
+            DynamicMenus = new ReadOnlyCollection<IDynamicMenuHandler>(dynamicMenus.ToList());
+        }
     }
 }