Index: DamEngine/trunk/src/Deltares.DamEngine.Interface/EngineInterface.cs
===================================================================
diff -u -r1553 -r1576
--- DamEngine/trunk/src/Deltares.DamEngine.Interface/EngineInterface.cs	(.../EngineInterface.cs)	(revision 1553)
+++ DamEngine/trunk/src/Deltares.DamEngine.Interface/EngineInterface.cs	(.../EngineInterface.cs)	(revision 1576)
@@ -156,10 +156,14 @@
             // already can be messages added by instantiation of the interface too. So add the local to the global
             if (validationMessages != null && validationMessages.Count > 0)
             {
-                DamProjectData.CalculationMessages.AddRange(validationMessages);
+                if (DamProjectData != null && DamProjectData.CalculationMessages != null)
+                {
+                    DamProjectData.CalculationMessages.AddRange(validationMessages);
+                }
             }
+
             // Now check if there are any messages at all, if so return them.
-            if (DamProjectData.CalculationMessages.Count > 0)
+            if (DamProjectData != null && DamProjectData.CalculationMessages != null && DamProjectData.CalculationMessages.Count > 0)
             {
                 Output output = FillXmlOutputFromDam.CreateOutput(DamProjectData);
                 string outputXml = DamXmlSerialization.SaveOutputAsXmlString(output);