Merge pull request #36 from RockLib/error

Add error event to receiver interface

RockLib.Messaging.Tests/FakeReceiver.cs

@@ -11,6 +11,7 @@ public class FakeReceiver : IReceiver
 
         public event EventHandler Connected;
         public event EventHandler<DisconnectedEventArgs> Disconnected;
+        public event EventHandler<ErrorEventArgs> Error;
 
         public void Dispose()
         {

RockLib.Messaging/ErrorEventArgs.cs

@@ -0,0 +1,31 @@
+using System;
+
+namespace RockLib.Messaging
+{
+    /// <summary>
+    /// Provides data for the <see cref="IReceiver.Error"/> event.
+    /// </summary>
+    public class ErrorEventArgs : EventArgs
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ErrorEventArgs"/> class.
+        /// </summary>
+        /// <param name="message">A message the describes the error.</param>
+        /// <param name="exception">The exception responsible for the error.</param>
+        public ErrorEventArgs(string message, Exception exception)
+        {
+            Message = message;
+            Exception = exception;
+        }
+
+        /// <summary>
+        /// Gets the message that describes the error.
+        /// </summary>
+        public string Message { get; }
+
+        /// <summary>
+        /// Gets the exception responsible for the error.
+        /// </summary>
+        public Exception Exception { get; }
+    }
+}

RockLib.Messaging/ForwardingReceiver.cs

@@ -193,6 +193,19 @@ public event EventHandler<DisconnectedEventArgs> Disconnected
             remove => Receiver.Disconnected -= value;
         }
 
+        /// <summary>
+        /// Occurs when an error happens.
+        /// <para>
+        /// This event passes through to the <see cref="IReceiver.Error"/> event of
+        /// the <see cref="Receiver"/> property.
+        /// </para>
+        /// </summary>
+        public event EventHandler<ErrorEventArgs> Error
+        {
+            add => Receiver.Error += value;
+            remove => Receiver.Error -= value;
+        }
+
         /// <summary>
         /// Disposes the <see cref="Receiver"/> property and, if they are not null,
         /// the <see cref="AcknowledgeForwarder"/>, <see cref="RollbackForwarder"/>,

RockLib.Messaging/IReceiver.cs

@@ -33,5 +33,10 @@ public interface IReceiver : IDisposable
         /// Occurs when a connection is lost.
         /// </summary>
         event EventHandler<DisconnectedEventArgs> Disconnected;
+
+        /// <summary>
+        /// Occurs when an error happens.
+        /// </summary>
+        event EventHandler<ErrorEventArgs> Error;
     }
 }

RockLib.Messaging/Receiver.cs

@@ -52,6 +52,11 @@ public IMessageHandler MessageHandler
         /// </summary>
         public event EventHandler<DisconnectedEventArgs> Disconnected;
 
+        /// <summary>
+        /// Occurs when an error happens.
+        /// </summary>
+        public event EventHandler<ErrorEventArgs> Error;
+
         /// <summary>
         /// Frees resources and stops receiving messages.
         /// </summary>
@@ -77,6 +82,13 @@ public void Dispose()
         /// <param name="errorMessage">The error message that describes the reason for the disconnection.</param>
         protected void OnDisconnected(string errorMessage) => Disconnected?.Invoke(this, new DisconnectedEventArgs(errorMessage));
 
+        /// <summary>
+        /// Invokes the <see cref="Error"/> event.
+        /// </summary>
+        /// <param name="message">A message the describes the error.</param>
+        /// <param name="exception">The exception responsible for the error.</param>
+        protected void OnError(string message, Exception exception) => Error?.Invoke(this, new ErrorEventArgs(message, exception));
+
         /// <summary>
         /// Unregisters all event handlers from the <see cref="Connected"/> and
         /// <see cref="Disconnected"/> events and sets <see cref="MessageHandler"/>