1 files changed, 100 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.Core/Messaging/IMessage.cs b/src/DotNetOpenAuth.Core/Messaging/IMessage.cs
new file mode 100644
index 0000000..e91a160
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+++ b/src/DotNetOpenAuth.Core/Messaging/IMessage.cs
@@ -0,0 +1,100 @@
+//-----------------------------------------------------------------------
+// <copyright file="IMessage.cs" company="Andrew Arnott">
+//     Copyright (c) Andrew Arnott. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace DotNetOpenAuth.Messaging {
+	using System;
+	using System.Collections.Generic;
+	using System.Diagnostics.Contracts;
+	using System.Text;
+
+	/// <summary>
+	/// The interface that classes must implement to be serialized/deserialized
+	/// as protocol or extension messages.
+	/// </summary>
+	[ContractClass(typeof(IMessageContract))]
+	public interface IMessage {
+		/// <summary>
+		/// Gets the version of the protocol or extension this message is prepared to implement.
+		/// </summary>
+		/// <remarks>
+		/// Implementations of this interface should ensure that this property never returns null.
+		/// </remarks>
+		Version Version { get; }
+
+		/// <summary>
+		/// Gets the extra, non-standard Protocol parameters included in the message.
+		/// </summary>
+		/// <remarks>
+		/// Implementations of this interface should ensure that this property never returns null.
+		/// </remarks>
+		IDictionary<string, string> ExtraData { get; }
+
+		/// <summary>
+		/// Checks the message state for conformity to the protocol specification
+		/// and throws an exception if the message is invalid.
+		/// </summary>
+		/// <remarks>
+		/// <para>Some messages have required fields, or combinations of fields that must relate to each other
+		/// in specialized ways.  After deserializing a message, this method checks the state of the 
+		/// message to see if it conforms to the protocol.</para>
+		/// <para>Note that this property should <i>not</i> check signatures or perform any state checks
+		/// outside this scope of this particular message.</para>
+		/// </remarks>
+		/// <exception cref="ProtocolException">Thrown if the message is invalid.</exception>
+		void EnsureValidMessage();
+	}
+
+	/// <summary>
+	/// Code contract for the <see cref="IMessage"/> interface.
+	/// </summary>
+	[ContractClassFor(typeof(IMessage))]
+	internal abstract class IMessageContract : IMessage {
+		/// <summary>
+		/// Prevents a default instance of the <see cref="IMessageContract"/> class from being created.
+		/// </summary>
+		private IMessageContract() {
+		}
+
+		/// <summary>
+		/// Gets the version of the protocol or extension this message is prepared to implement.
+		/// </summary>
+		Version IMessage.Version {
+			get {
+				Contract.Ensures(Contract.Result<Version>() != null);
+				return default(Version); // dummy return
+			}
+		}
+
+		/// <summary>
+		/// Gets the extra, non-standard Protocol parameters included in the message.
+		/// </summary>
+		/// <value></value>
+		/// <remarks>
+		/// Implementations of this interface should ensure that this property never returns null.
+		/// </remarks>
+		IDictionary<string, string> IMessage.ExtraData {
+			get {
+				Contract.Ensures(Contract.Result<IDictionary<string, string>>() != null);
+				return default(IDictionary<string, string>);
+			}
+		}
+
+		/// <summary>
+		/// Checks the message state for conformity to the protocol specification
+		/// and throws an exception if the message is invalid.
+		/// </summary>
+		/// <remarks>
+		/// 	<para>Some messages have required fields, or combinations of fields that must relate to each other
+		/// in specialized ways.  After deserializing a message, this method checks the state of the
+		/// message to see if it conforms to the protocol.</para>
+		/// 	<para>Note that this property should <i>not</i> check signatures or perform any state checks
+		/// outside this scope of this particular message.</para>
+		/// </remarks>
+		/// <exception cref="ProtocolException">Thrown if the message is invalid.</exception>
+		void IMessage.EnsureValidMessage() {
+		}
+	}
+}