Added filesystemchanged model

src/activities/Elsa.Activities.File/Models/FileSystemChanged.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Elsa.Activities.File.Models
+{
+    public class FileSystemChanged
+    {
+
+        public WatcherChangeTypes ChangeType { get; set; }
+
+        public string Directory { get; set; }
+
+        public string FileName { get; set; }
+    }
+}