Change GetAuthType to use a context object instead of a delegate.

src/Microsoft.AspNet.HttpFeature/Security/IAuthTypeContext.cs

@@ -0,0 +1,9 @@
+using System.Collections.Generic;
+
+namespace Microsoft.AspNet.HttpFeature.Security
+{
+    public interface IAuthTypeContext
+    {
+        void Ack(IDictionary<string,object> description);
+    }
+}

src/Microsoft.AspNet.HttpFeature/Security/IAuthenticationHandler.cs

@@ -3,13 +3,11 @@ using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.HttpFeature.Security
 {
-    public delegate void DescriptionDelegate(IDictionary<string, object> description, object state);
-
     public interface IAuthenticationHandler
     {
-        void GetDescriptions(DescriptionDelegate callback, object state);
+        void GetDescriptions(IAuthTypeContext context);
 
-        void Authenticate(IAuthenticateContext context); // TODO: (maybe?)
+        void Authenticate(IAuthenticateContext context);
         Task AuthenticateAsync(IAuthenticateContext context);
 
         void Challenge(IChallengeContext context);

src/Microsoft.AspNet.PipelineCore/DefaultHttpContext.cs

@@ -94,25 +94,17 @@ namespace Microsoft.AspNet.PipelineCore
             _features[type] = instance;
         }
 
-        // TODO: Use context, not a delegate, like all the other APIs
-        private static DescriptionDelegate GetAuthenticationTypesDelegate = GetAuthenticationTypesCallback;
-
         public override IEnumerable<AuthenticationDescription> GetAuthenticationTypes()
         {
-            // TODO: Use context, not a delegate, like all the other APIs
-            var descriptions = new List<AuthenticationDescription>();
             var handler = HttpAuthentication.Handler;
-            if (handler != null)
+            if (handler == null)
             {
-                handler.GetDescriptions(GetAuthenticationTypesDelegate, descriptions);
+                return new AuthenticationDescription[0];
             }
-            return descriptions;
-        }
 
-        private static void GetAuthenticationTypesCallback(IDictionary<string, object> description, object state)
-        {
-            var localDescriptions = (List<AuthenticationDescription>)state;
-            localDescriptions.Add(new AuthenticationDescription(description));
+            var authTypeContext = new AuthTypeContext();
+            handler.GetDescriptions(authTypeContext);
+            return authTypeContext.Results;
         }
 
         public override IEnumerable<AuthenticationResult> Authenticate(IList<string> authenticationTypes)

src/Microsoft.AspNet.PipelineCore/Security/AuthTypeContext.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using Microsoft.AspNet.Abstractions.Security;
+using Microsoft.AspNet.HttpFeature.Security;
+
+namespace Microsoft.AspNet.PipelineCore.Security
+{
+    public class AuthTypeContext : IAuthTypeContext
+    {
+        public AuthTypeContext()
+        {
+            Results = new List<AuthenticationDescription>();
+        }
+
+        public IList<AuthenticationDescription> Results { get; private set; }
+                
+        public void Ack(IDictionary<string, object> description)
+        {
+            Results.Add(new AuthenticationDescription(description));
+        }
+    }
+}