Refactored AX extension and the Associations collection to use KeyedCollection to simplify their code and API.

11 files changed, 124 insertions, 168 deletions

diff --git a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/AttributeExchangeRoundtripTests.cs b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/AttributeExchangeRoundtripTests.cs
index ac86156..1051092 100644
--- a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/AttributeExchangeRoundtripTests.cs
+++ b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/AttributeExchangeRoundtripTests.cs
@@ -19,12 +19,12 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions {
 		[TestMethod]
 		public void Fetch() {
 			var request = new FetchRequest();
-			request.AddAttribute(new AttributeRequest(NicknameTypeUri));
-			request.AddAttribute(new AttributeRequest(EmailTypeUri, false, int.MaxValue));
+			request.Attributes.Add(new AttributeRequest(NicknameTypeUri));
+			request.Attributes.Add(new AttributeRequest(EmailTypeUri, false, int.MaxValue));
 
 			var response = new FetchResponse();
-			response.AddAttribute(new AttributeValues(NicknameTypeUri, "Andrew"));
-			response.AddAttribute(new AttributeValues(EmailTypeUri, "a@a.com", "b@b.com"));
+			response.Attributes.Add(new AttributeValues(NicknameTypeUri, "Andrew"));
+			response.Attributes.Add(new AttributeValues(EmailTypeUri, "a@a.com", "b@b.com"));
 
 			ExtensionTestUtilities.Roundtrip(Protocol.Default, new[] { request }, new[] { response });
 		}
@@ -36,7 +36,7 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions {
 				IncrementingAttribute,
 				"val" + (incrementingAttributeValue++).ToString(),
 				"val" + (incrementingAttributeValue++).ToString());
-			request.AddAttribute(newAttribute);
+			request.Attributes.Add(newAttribute);
 
 			var successResponse = new StoreResponse();
 			successResponse.Succeeded = true;
diff --git a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchRequestTests.cs b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchRequestTests.cs
index 5374794..4dbb5ad 100644
--- a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchRequestTests.cs
+++ b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchRequestTests.cs
@@ -14,26 +14,26 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions {
 	public class FetchRequestTests : OpenIdTestBase {
 		[TestMethod, ExpectedException(typeof(ArgumentNullException))]
 		public void AddAttributeRequestNull() {
-			new FetchRequest().AddAttribute(null);
+			new FetchRequest().Attributes.Add(null);
 		}
 
 		[TestMethod]
 		public void AddAttributeRequest() {
 			var req = new FetchRequest();
-			req.AddAttribute(new AttributeRequest() { TypeUri = "http://someUri" });
+			req.Attributes.Add(new AttributeRequest() { TypeUri = "http://someUri" });
 		}
 
 		[TestMethod]
 		public void AddAttributeRequestStrangeUri() {
 			var req = new FetchRequest();
-			req.AddAttribute(new AttributeRequest() { TypeUri = "=someUri*who*knows*but*this*is*legal" });
+			req.Attributes.Add(new AttributeRequest() { TypeUri = "=someUri*who*knows*but*this*is*legal" });
 		}
 
 		[TestMethod, ExpectedException(typeof(ArgumentException))]
 		public void AddAttributeRequestAgain() {
 			var req = new FetchRequest();
-			req.AddAttribute(new AttributeRequest() { TypeUri = "http://UriTwice" });
-			req.AddAttribute(new AttributeRequest() { TypeUri = "http://UriTwice" });
+			req.Attributes.Add(new AttributeRequest() { TypeUri = "http://UriTwice" });
+			req.Attributes.Add(new AttributeRequest() { TypeUri = "http://UriTwice" });
 		}
 
 		[TestMethod]
@@ -86,13 +86,13 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions {
 			Assert.AreEqual(req1, req2);
 
 			// Add attributes in different orders deliberately.
-			req1.AddAttribute(new AttributeRequest("http://att1"));
+			req1.Attributes.Add(new AttributeRequest("http://att1"));
 			Assert.AreNotEqual(req1, req2);
-			req2.AddAttribute(new AttributeRequest("http://att2"));
+			req2.Attributes.Add(new AttributeRequest("http://att2"));
 			Assert.AreNotEqual(req1, req2);
-			req1.AddAttribute(new AttributeRequest("http://att2"));
+			req1.Attributes.Add(new AttributeRequest("http://att2"));
 			Assert.AreNotEqual(req1, req2);
-			req2.AddAttribute(new AttributeRequest("http://att1"));
+			req2.Attributes.Add(new AttributeRequest("http://att1"));
 			Assert.AreEqual(req1, req2);
 		}
 	}
diff --git a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchResponseTests.cs b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchResponseTests.cs
index 3f01498..32e723a 100644
--- a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchResponseTests.cs
+++ b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/FetchResponseTests.cs
@@ -15,27 +15,27 @@ namespace DotNetOpenId.Test.OpenId.Extensions {
 		[TestMethod]
 		public void AddAttribute() {
 			var response = new FetchResponse();
-			response.AddAttribute(new AttributeValues("http://someattribute", "Value1"));
+			response.Attributes.Add(new AttributeValues("http://someattribute", "Value1"));
 		}
 
 		[TestMethod]
 		public void AddTwoAttributes() {
 			var response = new FetchResponse();
-			response.AddAttribute(new AttributeValues("http://someattribute", "Value1"));
-			response.AddAttribute(new AttributeValues("http://someOtherAttribute", "Value2"));
+			response.Attributes.Add(new AttributeValues("http://someattribute", "Value1"));
+			response.Attributes.Add(new AttributeValues("http://someOtherAttribute", "Value2"));
 		}
 
 		[TestMethod, ExpectedException(typeof(ArgumentException))]
 		public void AddAttributeTwice() {
 			var response = new FetchResponse();
-			response.AddAttribute(new AttributeValues("http://someattribute", "Value1"));
-			response.AddAttribute(new AttributeValues("http://someattribute", "Value1"));
+			response.Attributes.Add(new AttributeValues("http://someattribute", "Value1"));
+			response.Attributes.Add(new AttributeValues("http://someattribute", "Value1"));
 		}
 
 		[TestMethod, ExpectedException(typeof(ArgumentNullException))]
 		public void AddAttributeNull() {
 			var response = new FetchResponse();
-			response.AddAttribute(null);
+			response.Attributes.Add(null);
 		}
 
 		[TestMethod]
@@ -50,13 +50,13 @@ namespace DotNetOpenId.Test.OpenId.Extensions {
 			Assert.AreEqual(response1, response2);
 
 			// Add attributes in different orders deliberately.
-			response1.AddAttribute(new AttributeValues("http://att1"));
+			response1.Attributes.Add(new AttributeValues("http://att1"));
 			Assert.AreNotEqual(response1, response2);
-			response2.AddAttribute(new AttributeValues("http://att2"));
+			response2.Attributes.Add(new AttributeValues("http://att2"));
 			Assert.AreNotEqual(response1, response2);
-			response1.AddAttribute(new AttributeValues("http://att2"));
+			response1.Attributes.Add(new AttributeValues("http://att2"));
 			Assert.AreNotEqual(response1, response2);
-			response2.AddAttribute(new AttributeValues("http://att1"));
+			response2.Attributes.Add(new AttributeValues("http://att1"));
 			Assert.AreEqual(response1, response2);
 		}
 	}
diff --git a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/StoreRequestTests.cs b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/StoreRequestTests.cs
index e0fe064..23c9177 100644
--- a/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/StoreRequestTests.cs
+++ b/src/DotNetOpenAuth.Test/OpenId/Extensions/AttributeExchange/StoreRequestTests.cs
@@ -31,7 +31,7 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions.AttributeExchange {
 		public void AddAttributeByValue() {
 			var req = new StoreRequest();
 			AttributeValues value = new AttributeValues();
-			req.AddAttribute(value);
+			req.Attributes.Add(value);
 			Assert.AreSame(value, req.Attributes.Single());
 		}
 
@@ -41,7 +41,7 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions.AttributeExchange {
 		[TestMethod]
 		public void AddAttributeByPrimitives() {
 			var req = new StoreRequest();
-			req.AddAttribute("http://att1", "value1", "value2");
+			req.Attributes.Add("http://att1", "value1", "value2");
 			AttributeValues value = req.Attributes.Single();
 			Assert.AreEqual("http://att1", value.TypeUri);
 			Assert.IsTrue(MessagingUtilities.AreEquivalent(new[] { "value1", "value2" }, value.Values));
@@ -57,13 +57,13 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions.AttributeExchange {
 			Assert.AreEqual(req1, req2);
 
 			// Add attributes in different orders deliberately.
-			req1.AddAttribute("http://att1");
+			req1.Attributes.Add("http://att1");
 			Assert.AreNotEqual(req1, req2);
-			req2.AddAttribute("http://att2");
+			req2.Attributes.Add("http://att2");
 			Assert.AreNotEqual(req1, req2);
-			req1.AddAttribute("http://att2");
+			req1.Attributes.Add("http://att2");
 			Assert.AreNotEqual(req1, req2);
-			req2.AddAttribute("http://att1");
+			req2.Attributes.Add("http://att1");
 			Assert.AreEqual(req1, req2);
 		}
 	}
diff --git a/src/DotNetOpenAuth/DotNetOpenAuth.csproj b/src/DotNetOpenAuth/DotNetOpenAuth.csproj
index 0e580e5..e63297f 100644
--- a/src/DotNetOpenAuth/DotNetOpenAuth.csproj
+++ b/src/DotNetOpenAuth/DotNetOpenAuth.csproj
@@ -215,6 +215,7 @@
     <Compile Include="Messaging\IMessageWithEvents.cs" />
     <Compile Include="Messaging\IProtocolMessageWithExtensions.cs" />
     <Compile Include="Messaging\InternalErrorException.cs" />
+    <Compile Include="Messaging\KeyedCollectionDelegate.cs" />
     <Compile Include="Messaging\NetworkDirectWebResponse.cs" />
     <Compile Include="Messaging\OutgoingWebResponseActionResult.cs" />
     <Compile Include="Messaging\Reflection\IMessagePartEncoder.cs" />
diff --git a/src/DotNetOpenAuth/Messaging/KeyedCollectionDelegate.cs b/src/DotNetOpenAuth/Messaging/KeyedCollectionDelegate.cs
new file mode 100644
index 0000000..928f873
--- /dev/null
+++ b/src/DotNetOpenAuth/Messaging/KeyedCollectionDelegate.cs
@@ -0,0 +1,45 @@
+//-----------------------------------------------------------------------
+// <copyright file="KeyedCollectionDelegate.cs" company="Andrew Arnott">
+//     Copyright (c) Andrew Arnott. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace DotNetOpenAuth.Messaging {
+	using System;
+	using System.Collections.ObjectModel;
+	using System.Diagnostics.Contracts;
+
+	/// <summary>
+	/// A KeyedCollection whose item -&gt; key transform is provided via a delegate
+	/// to its constructor, and null items are disallowed.
+	/// </summary>
+	/// <typeparam name="TKey">The type of the key.</typeparam>
+	/// <typeparam name="TItem">The type of the item.</typeparam>
+	internal class KeyedCollectionDelegate<TKey, TItem> : KeyedCollection<TKey, TItem> {
+		/// <summary>
+		/// The delegate that returns a key for the given item.
+		/// </summary>
+		private Func<TItem, TKey> getKeyForItemDelegate;
+
+		/// <summary>
+		/// Initializes a new instance of the KeyedCollectionDelegate class.
+		/// </summary>
+		/// <param name="getKeyForItemDelegate">The delegate that gets the key for a given item.</param>
+		internal KeyedCollectionDelegate(Func<TItem, TKey> getKeyForItemDelegate) {
+			Contract.Requires(getKeyForItemDelegate != null);
+			ErrorUtilities.VerifyArgumentNotNull(getKeyForItemDelegate, "getKeyForItemDelegate");
+
+			this.getKeyForItemDelegate = getKeyForItemDelegate;
+		}
+
+		/// <summary>
+		/// When implemented in a derived class, extracts the key from the specified element.
+		/// </summary>
+		/// <param name="item">The element from which to extract the key.</param>
+		/// <returns>The key for the specified element.</returns>
+		protected override TKey GetKeyForItem(TItem item) {
+			ErrorUtilities.VerifyArgumentNotNull(item, "item");
+			return this.getKeyForItemDelegate(item);
+		}
+	}
+}
diff --git a/src/DotNetOpenAuth/OpenId/Associations.cs b/src/DotNetOpenAuth/OpenId/Associations.cs
index 1fd6177..fe2be42 100644
--- a/src/DotNetOpenAuth/OpenId/Associations.cs
+++ b/src/DotNetOpenAuth/OpenId/Associations.cs
@@ -7,6 +7,7 @@
 namespace DotNetOpenAuth.OpenId {
 	using System;
 	using System.Collections.Generic;
+	using System.Collections.ObjectModel;
 	using System.Diagnostics;
 	using System.Linq;
 	using DotNetOpenAuth.Messaging;
@@ -25,13 +26,12 @@ namespace DotNetOpenAuth.OpenId {
 		/// The lookup table where keys are the association handles and values are the associations themselves.
 		/// </summary>
 		[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
-		private readonly Dictionary<string, Association> associations;
+		private readonly KeyedCollection<string, Association> associations = new KeyedCollectionDelegate<string, Association>(assoc => assoc.Handle);
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="Associations"/> class.
 		/// </summary>
 		public Associations() {
-			this.associations = new Dictionary<string, Association>();
 		}
 
 		/// <summary>
@@ -45,7 +45,7 @@ namespace DotNetOpenAuth.OpenId {
 		public IEnumerable<Association> Best {
 			get {
 				lock (this.associations) {
-					return this.associations.Values.OrderByDescending(assoc => assoc.Issued);
+					return this.associations.OrderByDescending(assoc => assoc.Issued);
 				}
 			}
 		}
@@ -57,7 +57,8 @@ namespace DotNetOpenAuth.OpenId {
 		public void Set(Association association) {
 			ErrorUtilities.VerifyArgumentNotNull(association, "association");
 			lock (this.associations) {
-				this.associations[association.Handle] = association;
+				this.associations.Remove(association.Handle); // just in case one already exists.
+				this.associations.Add(association);
 			}
 		}
 
@@ -68,9 +69,11 @@ namespace DotNetOpenAuth.OpenId {
 		/// <returns>The desired association, or null if none with the given handle could be found.</returns>
 		public Association Get(string handle) {
 			lock (this.associations) {
-				Association assoc;
-				this.associations.TryGetValue(handle, out assoc);
-				return assoc;
+				if (this.associations.Contains(handle)) {
+					return this.associations[handle];
+				} else {
+					return null;
+				}
 			}
 		}
 
@@ -90,7 +93,7 @@ namespace DotNetOpenAuth.OpenId {
 		/// </summary>
 		public void ClearExpired() {
 			lock (this.associations) {
-				var expireds = this.associations.Values.Where(assoc => assoc.IsExpired).ToList();
+				var expireds = this.associations.Where(assoc => assoc.IsExpired).ToList();
 				foreach (Association assoc in expireds) {
 					this.associations.Remove(assoc.Handle);
 				}
diff --git a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/AXUtilities.cs b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/AXUtilities.cs
index 53b916f..3504b7a 100644
--- a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/AXUtilities.cs
+++ b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/AXUtilities.cs
@@ -7,13 +7,27 @@
 namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 	using System;
 	using System.Collections.Generic;
+	using System.Diagnostics.Contracts;
 	using System.Globalization;
 	using DotNetOpenAuth.Messaging;
 
 	/// <summary>
 	/// Helper methods shared by multiple messages in the Attribute Exchange extension.
 	/// </summary>
-	internal static class AXUtilities {
+	public static class AXUtilities {
+		/// <summary>
+		/// Adds a given attribute with one or more values to the request for storage.
+		/// Applicable to Relying Parties only.
+		/// </summary>
+		/// <param name="collection">The collection of <see cref="AttributeValues"/> to add to.</param>
+		/// <param name="typeUri">The type URI of the attribute.</param>
+		/// <param name="values">The attribute values.</param>
+		public static void Add(this ICollection<AttributeValues> collection, string typeUri, params string[] values) {
+			Contract.Requires(collection != null);
+			ErrorUtilities.VerifyArgumentNotNull(collection, "collection");
+			collection.Add(new AttributeValues(typeUri, values));
+		}
+
 		/// <summary>
 		/// Serializes a set of attribute values to a dictionary of fields to send in the message.
 		/// </summary>
diff --git a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchRequest.cs b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchRequest.cs
index 0f5e4e6..72f98ee 100644
--- a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchRequest.cs
+++ b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchRequest.cs
@@ -7,6 +7,7 @@
 namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 	using System;
 	using System.Collections.Generic;
+	using System.Collections.ObjectModel;
 	using System.Globalization;
 	using System.Linq;
 	using DotNetOpenAuth.Messaging;
@@ -48,9 +49,9 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		private const string Mode = "fetch_request";
 
 		/// <summary>
-		/// The list of requested attributes.  This field will never be null.
+		/// The collection of requested attributes.
 		/// </summary>
-		private readonly List<AttributeRequest> attributesRequested = new List<AttributeRequest>();
+		private readonly KeyedCollection<string, AttributeRequest> attributes = new KeyedCollectionDelegate<string, AttributeRequest>(ar => ar.TypeUri);
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="FetchRequest"/> class.
@@ -60,10 +61,13 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		}
 
 		/// <summary>
-		/// Gets a sequence of the attributes whose values are requested by the Relying Party.
+		/// Gets a collection of the attributes whose values are 
+		/// requested by the Relying Party.
 		/// </summary>
-		public IEnumerable<AttributeRequest> Attributes {
-			get { return this.attributesRequested; }
+		/// <value>A collection where the keys are the attribute type URIs, and the value
+		/// is all the attribute request details.</value>
+		public KeyedCollection<string, AttributeRequest> Attributes {
+			get { return this.attributes; }
 		}
 
 		/// <summary>
@@ -90,29 +94,6 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		private string RequiredAliases { get; set; }
 
 		/// <summary>
-		/// Adds a request for the values of a given attribute.
-		/// Applicable to Relying Parties.
-		/// </summary>
-		/// <param name="attribute">The attribute.</param>
-		public void AddAttribute(AttributeRequest attribute) {
-			ErrorUtilities.VerifyArgumentNotNull(attribute, "attribute");
-			ErrorUtilities.VerifyArgumentNamed(!this.ContainsAttribute(attribute.TypeUri), "attribute", OpenIdStrings.AttributeAlreadyAdded, attribute.TypeUri);
-			this.attributesRequested.Add(attribute);
-		}
-
-		/// <summary>
-		/// Find out whether the value(s) of a given attribute are being requested by the Relying Party.
-		/// Applicable to Providers.
-		/// </summary>
-		/// <param name="attributeTypeUri">The type URI of the attribute.</param>
-		/// <returns>
-		/// The details of a Relying Party's request for the given attribute; or <c>null</c> if the relyign party did not ask for the values of the given attribute.
-		/// </returns>
-		public AttributeRequest GetAttribute(string attributeTypeUri) {
-			return this.attributesRequested.SingleOrDefault(attribute => string.Equals(attribute.TypeUri, attributeTypeUri, StringComparison.Ordinal));
-		}
-
-		/// <summary>
 		/// Determines whether the specified <see cref="T:System.Object"/> is equal to the current <see cref="T:System.Object"/>.
 		/// </summary>
 		/// <param name="obj">The <see cref="T:System.Object"/> to compare with the current <see cref="T:System.Object"/>.</param>
@@ -177,7 +158,7 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 
 			List<string> requiredAliases = new List<string>(), optionalAliases = new List<string>();
 			AliasManager aliasManager = new AliasManager();
-			foreach (var att in this.attributesRequested) {
+			foreach (var att in this.attributes) {
 				string alias = aliasManager.GetAlias(att.TypeUri);
 
 				// define the alias<->typeUri mapping
@@ -240,7 +221,7 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 					} else {
 						att.Count = 1;
 					}
-					this.AddAttribute(att);
+					this.Attributes.Add(att);
 				} else {
 					Logger.OpenId.Error("Type URI definition of alias " + alias + " is missing.");
 				}
@@ -296,16 +277,5 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 
 			return aliasList.Split(',');
 		}
-
-		/// <summary>
-		/// Determines whether some attribute has values in this fetch request.
-		/// </summary>
-		/// <param name="typeUri">The type URI of the attribute in question.</param>
-		/// <returns>
-		/// 	<c>true</c> if the specified attribute appears in the fetch request; otherwise, <c>false</c>.
-		/// </returns>
-		private bool ContainsAttribute(string typeUri) {
-			return this.GetAttribute(typeUri) != null;
-		}
 	}
 }
diff --git a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchResponse.cs b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchResponse.cs
index c309532..0f7d40f 100644
--- a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchResponse.cs
+++ b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/FetchResponse.cs
@@ -6,9 +6,7 @@
 
 namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 	using System;
-	using System.Collections.Generic;
-	using System.Diagnostics;
-	using System.Globalization;
+	using System.Collections.ObjectModel;
 	using System.Linq;
 	using DotNetOpenAuth.Messaging;
 	using DotNetOpenAuth.OpenId.Messages;
@@ -39,9 +37,9 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		private const string Mode = "fetch_response";
 
 		/// <summary>
-		/// The list of provided attributes.  This field will never be null.
+		/// The collection of provided attributes.  This field will never be null.
 		/// </summary>
-		private readonly List<AttributeValues> attributesProvided = new List<AttributeValues>();
+		private readonly KeyedCollection<string, AttributeValues> attributesProvided = new KeyedCollectionDelegate<string, AttributeValues>(av => av.TypeUri);
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="FetchResponse"/> class.
@@ -53,7 +51,7 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		/// <summary>
 		/// Gets a sequence of the attributes whose values are provided by the OpenID Provider.
 		/// </summary>
-		public IEnumerable<AttributeValues> Attributes {
+		public KeyedCollection<string, AttributeValues> Attributes {
 			get { return this.attributesProvided; }
 		}
 
@@ -73,28 +71,6 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		public Uri UpdateUrl { get; set; }
 
 		/// <summary>
-		/// Adds attributes to the response for the relying party.
-		/// Applicable to Providers.
-		/// </summary>
-		/// <param name="attribute">The attribute and values to add to the response.</param>
-		public void AddAttribute(AttributeValues attribute) {
-			ErrorUtilities.VerifyArgumentNotNull(attribute, "attribute");
-			ErrorUtilities.VerifyArgumentNamed(!this.ContainsAttribute(attribute.TypeUri), "attribute", OpenIdStrings.AttributeAlreadyAdded, attribute.TypeUri);
-			this.attributesProvided.Add(attribute);
-		}
-
-		/// <summary>
-		/// Gets the value(s) returned by the OpenID Provider
-		/// for a given attribute, or null if that attribute was not provided.
-		/// Applicable to Relying Parties.
-		/// </summary>
-		/// <param name="attributeTypeUri">The type URI of the attribute.</param>
-		/// <returns>The values given by the Provider for the given attribute; or <c>null</c> if the attribute was not included in the message.</returns>
-		public AttributeValues GetAttribute(string attributeTypeUri) {
-			return this.attributesProvided.SingleOrDefault(attribute => string.Equals(attribute.TypeUri, attributeTypeUri, StringComparison.Ordinal));
-		}
-
-		/// <summary>
 		/// Determines whether the specified <see cref="T:System.Object"/> is equal to the current <see cref="T:System.Object"/>.
 		/// </summary>
 		/// <param name="obj">The <see cref="T:System.Object"/> to compare with the current <see cref="T:System.Object"/>.</param>
@@ -165,7 +141,7 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		void IMessageWithEvents.OnReceiving() {
 			var extraData = ((IMessage)this).ExtraData;
 			foreach (var att in AXUtilities.DeserializeAttributes(extraData)) {
-				this.AddAttribute(att);
+				this.Attributes.Add(att);
 			}
 		}
 
@@ -191,16 +167,5 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 				Logger.OpenId.ErrorFormat("The AX fetch response update_url parameter was not absolute ('{0}').  Ignoring value.", this.UpdateUrl);
 			}
 		}
-
-		/// <summary>
-		/// Determines whether some attribute has values in this fetch response.
-		/// </summary>
-		/// <param name="typeUri">The type URI of the attribute in question.</param>
-		/// <returns>
-		/// 	<c>true</c> if the specified attribute appears in the fetch response; otherwise, <c>false</c>.
-		/// </returns>
-		private bool ContainsAttribute(string typeUri) {
-			return this.GetAttribute(typeUri) != null;
-		}
 	}
 }
diff --git a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/StoreRequest.cs b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/StoreRequest.cs
index b4df366..e3743e4 100644
--- a/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/StoreRequest.cs
+++ b/src/DotNetOpenAuth/OpenId/Extensions/AttributeExchange/StoreRequest.cs
@@ -6,7 +6,7 @@
 
 namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 	using System;
-	using System.Collections.Generic;
+	using System.Collections.ObjectModel;
 	using System.Linq;
 	using DotNetOpenAuth.Messaging;
 	using DotNetOpenAuth.OpenId.Messages;
@@ -37,9 +37,9 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		private const string Mode = "store_request";
 
 		/// <summary>
-		/// The list of provided attribute values.  This field will never be null.
+		/// The collection of provided attribute values.  This field will never be null.
 		/// </summary>
-		private readonly List<AttributeValues> attributesProvided = new List<AttributeValues>();
+		private readonly KeyedCollection<string, AttributeValues> attributesProvided = new KeyedCollectionDelegate<string, AttributeValues>(av => av.TypeUri);
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="StoreRequest"/> class.
@@ -49,43 +49,12 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		}
 
 		/// <summary>
-		/// Gets a list of all the attributes that are included in the store request.
+		/// Gets the collection of all the attributes that are included in the store request.
 		/// </summary>
-		public IEnumerable<AttributeValues> Attributes {
+		public KeyedCollection<string, AttributeValues> Attributes {
 			get { return this.attributesProvided; }
 		}
 
-		/// <summary>
-		/// Adds a given attribute with one or more values to the request for storage.
-		/// Applicable to Relying Parties only.
-		/// </summary>
-		/// <param name="attribute">The attribute values.</param>
-		public void AddAttribute(AttributeValues attribute) {
-			ErrorUtilities.VerifyArgumentNotNull(attribute, "attribute");
-			ErrorUtilities.VerifyArgumentNamed(!this.ContainsAttribute(attribute.TypeUri), "attribute", OpenIdStrings.AttributeAlreadyAdded, attribute.TypeUri);
-			this.attributesProvided.Add(attribute);
-		}
-
-		/// <summary>
-		/// Adds a given attribute with one or more values to the request for storage.
-		/// Applicable to Relying Parties only.
-		/// </summary>
-		/// <param name="typeUri">The type URI of the attribute.</param>
-		/// <param name="values">The attribute values.</param>
-		public void AddAttribute(string typeUri, params string[] values) {
-			this.AddAttribute(new AttributeValues(typeUri, values));
-		}
-
-		/// <summary>
-		/// Gets the value(s) associated with a given attribute that should be stored.
-		/// Applicable to Providers only.
-		/// </summary>
-		/// <param name="attributeTypeUri">The type URI of the attribute whose values are being sought.</param>
-		/// <returns>The attribute values.</returns>
-		public AttributeValues GetAttribute(string attributeTypeUri) {
-			return this.attributesProvided.SingleOrDefault(attribute => string.Equals(attribute.TypeUri, attributeTypeUri, StringComparison.Ordinal));
-		}
-
 		#region IMessageWithEvents Members
 
 		/// <summary>
@@ -106,7 +75,7 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 		void IMessageWithEvents.OnReceiving() {
 			var fields = ((IMessage)this).ExtraData;
 			foreach (var att in AXUtilities.DeserializeAttributes(fields)) {
-				this.AddAttribute(att);
+				this.Attributes.Add(att);
 			}
 		}
 
@@ -154,16 +123,5 @@ namespace DotNetOpenAuth.OpenId.Extensions.AttributeExchange {
 				return hashCode;
 			}
 		}
-
-		/// <summary>
-		/// Determines whether some attribute has values in this store request.
-		/// </summary>
-		/// <param name="typeUri">The type URI of the attribute in question.</param>
-		/// <returns>
-		/// 	<c>true</c> if the specified attribute appears in the store request; otherwise, <c>false</c>.
-		/// </returns>
-		private bool ContainsAttribute(string typeUri) {
-			return this.GetAttribute(typeUri) != null;
-		}
 	}
 }