Added basic device event handling.

src/NTwain/DeviceEventArgs.cs

@@ -0,0 +1,17 @@
+using NTwain.Data;
+using System;
+
+namespace NTwain
+{
+	/// <summary>
+	/// Contains data for a TWAIN source event.
+	/// </summary>
+	public class DeviceEventArgs : EventArgs
+	{
+		/// <summary>
+		/// Gets the detailed device event.
+		/// </summary>
+		/// <value>The device event.</value>
+		public TW_DEVICEEVENT Data { get; internal set; }
+	}
+}

src/NTwain/Triplets/DGControl.DeviceEvent.cs

@@ -0,0 +1,16 @@
+using NTwain.Data;
+using NTwain.Internals;
+
+namespace NTwain.Triplets
+{
+	sealed class DeviceEvent : BaseTriplet
+	{
+		internal DeviceEvent(TwainSession session) : base(session) { }
+    
+        public ReturnCode Get(ref TW_DEVICEEVENT sourceDeviceEvent)
+		{
+			return NativeMethods.DsmWin32(Session.Config.AppWin32, Session.CurrentSource.Identity, 
+                DataGroups.Control, DataArgumentType.DeviceEvent, Message.Get, ref sourceDeviceEvent);
+		}
+	}
+}

src/NTwain/Triplets/DGControl.cs

@@ -30,5 +30,8 @@ namespace NTwain.Triplets
 
         Status _status;
         internal Status Status => _status ?? (_status = new Status(Session));
+
+        DeviceEvent _devEvent;
+        internal DeviceEvent DeviceEvent => _devEvent ?? (_devEvent = new DeviceEvent(Session));
     }
 }

src/NTwain/TwainSession.MsgHandling.cs

@@ -15,7 +15,23 @@ namespace NTwain
     {
         private void HandleSourceMsg(Message msg)
         {
-            
+            switch (msg)
+            {
+                case Message.DeviceEvent:
+                    TW_DEVICEEVENT de = default;
+                    var rc = DGControl.DeviceEvent.Get(ref de);
+                    if (rc == ReturnCode.Success)
+                    {
+                        OnDeviceEvent(new DeviceEventArgs { Data = de });
+                    }
+                    break;
+                case Message.XferReady:
+                    break;
+                case Message.CloseDSReq:
+                    break;
+                case Message.CloseDSOK:
+                    break;
+            }
         }
     }
 }

src/NTwain/TwainSession.Props.cs

@@ -48,6 +48,26 @@ namespace NTwain
         public DGCustom DGCustom { get; set; }
 
 
+
+
+        /// <summary>
+        /// Occurs when the source has generated an event.
+        /// </summary>
+        public event EventHandler<DeviceEventArgs> DeviceEvent;
+
+        /// <summary>
+        /// Raises the <see cref="DeviceEvent"/> event.
+        /// </summary>
+        /// <param name="e"></param>
+        protected virtual void OnDeviceEvent(DeviceEventArgs e)
+        {
+            OnDeviceEvent(e);
+            DeviceEvent?.Invoke(this, e);
+        }
+
+
+
+
         /// <summary>
         /// Occurs when a property value changes.
         /// </summary>