Reduce allocation in OptionsManager

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

@@ -15,7 +15,7 @@ public class OptionsCache<[DynamicallyAccessedMembers(Options.DynamicallyAccesse
         IOptionsMonitorCache<TOptions>
         where TOptions : class
     {
-        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal);
+        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(concurrencyLevel: 1, capacity: 31, StringComparer.Ordinal); // 31 == default capacity
 
         /// <summary>
         /// Clears all options instances from the cache.
@@ -38,6 +38,24 @@ public virtual TOptions GetOrAdd(string name, Func<TOptions> createOptions)
             return _cache.GetOrAdd(name, new Lazy<TOptions>(createOptions)).Value;
         }
 
+        /// <summary>
+        /// Gets a named options instance, if available.
+        /// </summary>
+        /// <param name="name">The name of the options instance.</param>
+        /// <param name="options">The options instance.</param>
+        /// <returns>true if the options were retrieved; otherwise, false.</returns>
+        internal bool TryGetValue(string name, out TOptions options)
+        {
+            if (_cache.TryGetValue(name ?? Options.DefaultName, out Lazy<TOptions> lazy))
+            {
+                options = lazy.Value;
+                return true;
+            }
+
+            options = default;
+            return false;
+        }
+
         /// <summary>
         /// Tries to adds a new option to the cache, will return false if the name already exists.
         /// </summary>

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

@@ -29,13 +29,7 @@ public OptionsManager(IOptionsFactory<TOptions> factory)
         /// <summary>
         /// The default configured <typeparamref name="TOptions"/> instance, equivalent to Get(Options.DefaultName).
         /// </summary>
-        public TOptions Value
-        {
-            get
-            {
-                return Get(Options.DefaultName);
-            }
-        }
+        public TOptions Value => Get(Options.DefaultName);
 
         /// <summary>
         /// Returns a configured <typeparamref name="TOptions"/> instance with the given <paramref name="name"/>.
@@ -44,8 +38,15 @@ public virtual TOptions Get(string name)
         {
             name = name ?? Options.DefaultName;
 
-            // Store the options in our instance cache
-            return _cache.GetOrAdd(name, () => _factory.Create(name));
+            if (!_cache.TryGetValue(name, out TOptions options))
+            {
+                // Store the options in our instance cache. Avoid closure on fast path by storing state into scoped locals.
+                IOptionsFactory<TOptions> localFactory = _factory;
+                string localName = name;
+                options = _cache.GetOrAdd(name, () => localFactory.Create(localName));
+            }
+
+            return options;
         }
     }
 }