Add MetadataCollection

src/Microsoft.AspNetCore.Dispatcher.Abstractions/Address.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Collections.Generic;
 using System.Diagnostics;
 
 namespace Microsoft.AspNetCore.Dispatcher
@@ -11,6 +10,6 @@ namespace Microsoft.AspNetCore.Dispatcher
     {
         public abstract string DisplayName { get; }
 
-        public abstract IReadOnlyList<object> Metadata { get; }
+        public abstract MetadataCollection Metadata { get; }
     }
 }

src/Microsoft.AspNetCore.Dispatcher.Abstractions/Endpoint.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Collections.Generic;
 using System.Diagnostics;
 
 namespace Microsoft.AspNetCore.Dispatcher
@@ -11,6 +10,6 @@ namespace Microsoft.AspNetCore.Dispatcher
     {
         public abstract string DisplayName { get; }
 
-        public abstract IReadOnlyList<object> Metadata { get; }
+        public abstract MetadataCollection Metadata { get; }
     }
 }

src/Microsoft.AspNetCore.Dispatcher.Abstractions/MetadataCollection.cs

@@ -0,0 +1,104 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Dispatcher
+{
+    public class MetadataCollection : IReadOnlyList<object>
+    {
+        private readonly object[] _items;
+
+        public MetadataCollection()
+        {
+            _items = Array.Empty<object>();
+        }
+
+        public MetadataCollection(IEnumerable<object> items)
+        {
+            if (items == null)
+            {
+                throw new ArgumentNullException(nameof(items));
+            }
+
+            _items = items.ToArray();
+        }
+
+        public object this[int index] => _items[index];
+
+        public int Count => _items.Length;
+
+        public T GetMetadata<T>() where T : class
+        {
+            for (var i = _items.Length -1; i >= 0; i--)
+            {
+                var item = _items[i] as T;
+                if (item !=null)
+                {
+                    return item;
+                }
+            }
+
+            return default;
+        }
+
+        public IEnumerable<T> GetOrderedMetadata<T>() where T : class
+        {
+            for (var i = 0; i < _items.Length; i++)
+            {
+                var item = _items[i] as T;
+                if (item != null)
+                {
+                    yield return item;
+                }
+            }
+        }
+
+        public Enumerator GetEnumerator() => new Enumerator(this);
+
+        IEnumerator<object> IEnumerable<object>.GetEnumerator() => GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+        public struct Enumerator : IEnumerator<object>
+        {
+            private object[] _items;
+            private int _index;
+            private object _current;
+
+            internal Enumerator(MetadataCollection collection)
+            {
+                _items = collection._items;
+                _index = 0;
+                _current = null;
+            }
+
+            public object Current => _current;
+
+            public void Dispose()
+            {
+            }
+
+            public bool MoveNext()
+            {
+                if (_index < _items.Length)
+                {
+                    _current = _items[_index++];
+                    return true;
+                }
+
+                _current = null;
+                return false;
+            }
+
+            public void Reset()
+            {
+                _index = 0;
+                _current = null;
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Dispatcher/TemplateAddress.cs

@@ -29,12 +29,12 @@ namespace Microsoft.AspNetCore.Dispatcher
             Template = template;
             Defaults = new DispatcherValueCollection(values);
             DisplayName = displayName;
-            Metadata = metadata.ToArray();
+            Metadata = new MetadataCollection(metadata);
         }
 
         public override string DisplayName { get; }
 
-        public override IReadOnlyList<object> Metadata { get; }
+        public override MetadataCollection Metadata { get; }
 
         public string Template { get; }
 

src/Microsoft.AspNetCore.Dispatcher/TemplateEndpoint.cs

@@ -78,7 +78,7 @@ namespace Microsoft.AspNetCore.Dispatcher
             HttpMethod = httpMethod;
             HandlerFactory = (next) => requestDelegate;
             DisplayName = displayName;
-            Metadata = metadata.ToArray();
+            Metadata = new MetadataCollection(metadata);
         }
 
         public TemplateEndpoint(
@@ -109,14 +109,14 @@ namespace Microsoft.AspNetCore.Dispatcher
             HttpMethod = httpMethod;
             HandlerFactory = delegateFactory;
             DisplayName = displayName;
-            Metadata = metadata.ToArray();
+            Metadata = new MetadataCollection(metadata);
         }
 
         public override string DisplayName { get; }
 
         public string HttpMethod { get; }
 
-        public override IReadOnlyList<object> Metadata { get; }
+        public override MetadataCollection Metadata { get; }
 
         public Func<RequestDelegate, RequestDelegate> HandlerFactory { get; }
 

test/Microsoft.AspNetCore.Dispatcher.Abstractions.Test/MetadataCollectionTest.cs

@@ -0,0 +1,79 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Linq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Dispatcher
+{
+    public class MetadataCollectionTest
+    {
+        [Fact]
+        public void GetMetadata_ReturnsLastMatch()
+        {
+            // Arrange
+            var items = new object[]
+            {
+                new AuthNMetadata(),
+                new AuthZMetadata(),
+                new AuthNMetadata(),
+            };
+
+            var collection = new MetadataCollection(items);
+
+            // Act
+            var result = collection.GetMetadata<AuthNMetadata>();
+
+            // Assert
+            Assert.Same(items[2], result);
+        }
+
+        [Fact]
+        public void GetOrderedMetadata_ReturnsAllMatches()
+        {
+            // Arrange
+            var items = new object[]
+            {
+                new AuthNMetadata(),
+                new AuthZMetadata(),
+                new AuthNMetadata(),
+            };
+
+            var collection = new MetadataCollection(items);
+
+            // Act
+            var result = collection.GetOrderedMetadata<AuthNMetadata>();
+
+            // Assert
+            Assert.Equal(new object[] { items[0], items[2] }, result);
+        }
+
+        [Fact]
+        public void GetEnumerator_IncludesAllItems()
+        {
+            // Arrange
+            var items = new object[]
+            {
+                new AuthNMetadata(),
+                new AuthZMetadata(),
+                new AuthNMetadata(),
+            };
+
+            var collection = new MetadataCollection(items);
+
+            // Act
+            var result = collection.ToArray();
+
+            // Assert
+            Assert.Equal(items, result);
+        }
+
+        private class AuthNMetadata
+        {
+        }
+
+        private class AuthZMetadata
+        {
+        }
+    }
+}