Slimmer IOptions<T>

- Use a Lazy instead of the IOptionsCache (which is a concurrent dictionary)

Author: davidfowl

src/libraries/Microsoft.Extensions.Options/src/OptionsServiceCollectionExtensions.cs

@@ -26,7 +26,7 @@ public static IServiceCollection AddOptions(this IServiceCollection services)
                 throw new ArgumentNullException(nameof(services));
             }
 
-            services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(OptionsManager<>)));
+            services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(UnnamedOptionsManager<>)));
             services.TryAdd(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<>), typeof(OptionsManager<>)));
             services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>)));
             services.TryAdd(ServiceDescriptor.Transient(typeof(IOptionsFactory<>), typeof(OptionsFactory<>)));

src/libraries/Microsoft.Extensions.Options/src/UnnamedOptionsManager.cs

@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.Extensions.Options
+{
+    internal class UnnamedOptionsManager<[DynamicallyAccessedMembers(Options.DynamicallyAccessedMembers)] TOptions> :
+        IOptions<TOptions>
+        where TOptions : class
+    {
+        private readonly Lazy<TOptions> _lazy;
+
+        public UnnamedOptionsManager(IOptionsFactory<TOptions> factory)
+        {
+            _lazy = new Lazy<TOptions>(() => factory.Create(Options.DefaultName));
+        }
+
+        /// <summary>
+        /// The default configured <typeparamref name="TOptions"/> instance, equivalent to Get(Options.DefaultName).
+        /// </summary>
+        public TOptions Value => _lazy.Value;
+    }
+}