trying to merge identity in api

Sledgemapper.Api/Helpers/AppException.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Globalization;
+
+namespace Sledgemapper.Helpers
+{
+    // Custom exception class for throwing application specific exceptions (e.g. for validation) 
+    // that can be caught and handled within the application
+    public class AppException : Exception
+    {
+        public AppException() : base() {}
+
+        public AppException(string message) : base(message) { }
+
+        public AppException(string message, params object[] args) 
+            : base(String.Format(CultureInfo.CurrentCulture, message, args))
+        {
+        }
+    }
+}