1 files changed, 24 insertions, 6 deletions
diff --git a/src/DotNetOpenAuth.Core/Messaging/Bindings/StandardExpirationBindingElement.cs b/src/DotNetOpenAuth.Core/Messaging/Bindings/StandardExpirationBindingElement.cs
index 7ab78db..f19d4bd 100644
--- a/src/DotNetOpenAuth.Core/Messaging/Bindings/StandardExpirationBindingElement.cs
+++ b/src/DotNetOpenAuth.Core/Messaging/Bindings/StandardExpirationBindingElement.cs
@@ -6,6 +6,8 @@
 
 namespace DotNetOpenAuth.Messaging.Bindings {
 	using System;
+	using System.Threading;
+	using System.Threading.Tasks;
 	using DotNetOpenAuth.Configuration;
 
 	/// <summary>
@@ -14,6 +16,16 @@ namespace DotNetOpenAuth.Messaging.Bindings {
 	/// </summary>
 	internal class StandardExpirationBindingElement : IChannelBindingElement {
 		/// <summary>
+		/// A reusable pre-completed task that may be returned multiple times to reduce GC pressure.
+		/// </summary>
+		private static readonly Task<MessageProtections?> NullTask = Task.FromResult<MessageProtections?>(null);
+
+		/// <summary>
+		/// A reusable pre-completed task that may be returned multiple times to reduce GC pressure.
+		/// </summary>
+		private static readonly Task<MessageProtections?> CompletedExpirationTask = Task.FromResult<MessageProtections?>(MessageProtections.Expiration);
+
+		/// <summary>
 		/// Initializes a new instance of the <see cref="StandardExpirationBindingElement"/> class.
 		/// </summary>
 		internal StandardExpirationBindingElement() {
@@ -51,24 +63,30 @@ namespace DotNetOpenAuth.Messaging.Bindings {
 		/// Sets the timestamp on an outgoing message.
 		/// </summary>
 		/// <param name="message">The outgoing message.</param>
+		/// <param name="cancellationToken">The cancellation token.</param>
 		/// <returns>
 		/// The protections (if any) that this binding element applied to the message.
 		/// Null if this binding element did not even apply to this binding element.
 		/// </returns>
-		public MessageProtections? ProcessOutgoingMessage(IProtocolMessage message) {
+		/// <remarks>
+		/// Implementations that provide message protection must honor the
+		/// <see cref="MessagePartAttribute.RequiredProtection" /> properties where applicable.
+		/// </remarks>
+		public Task<MessageProtections?> ProcessOutgoingMessageAsync(IProtocolMessage message, CancellationToken cancellationToken) {
 			IExpiringProtocolMessage expiringMessage = message as IExpiringProtocolMessage;
 			if (expiringMessage != null) {
 				expiringMessage.UtcCreationDate = DateTime.UtcNow;
-				return MessageProtections.Expiration;
+				return CompletedExpirationTask;
 			}
 
-			return null;
+			return NullTask;
 		}
 
 		/// <summary>
 		/// Reads the timestamp on a message and throws an exception if the message is too old.
 		/// </summary>
 		/// <param name="message">The incoming message.</param>
+		/// <param name="cancellationToken">The cancellation token.</param>
 		/// <returns>
 		/// The protections (if any) that this binding element applied to the message.
 		/// Null if this binding element did not even apply to this binding element.
@@ -78,7 +96,7 @@ namespace DotNetOpenAuth.Messaging.Bindings {
 		/// Thrown when the binding element rules indicate that this message is invalid and should
 		/// NOT be processed.
 		/// </exception>
-		public MessageProtections? ProcessIncomingMessage(IProtocolMessage message) {
+		public Task<MessageProtections?> ProcessIncomingMessageAsync(IProtocolMessage message, CancellationToken cancellationToken) {
 			IExpiringProtocolMessage expiringMessage = message as IExpiringProtocolMessage;
 			if (expiringMessage != null) {
 				// Yes the UtcCreationDate is supposed to always be in UTC already,
@@ -96,10 +114,10 @@ namespace DotNetOpenAuth.Messaging.Bindings {
 					MessagingStrings.MessageTimestampInFuture,
 					creationDate);
 
-				return MessageProtections.Expiration;
+				return CompletedExpirationTask;
 			}
 
-			return null;
+			return NullTask;
 		}
 
 		#endregion