Index: Application/Ringtoets/src/Application.Ringtoets.Storage/Read/GrassCoverErosionInwards/GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions.cs
===================================================================
diff -u -r8cb270db5fbcb82f19d6f3a390f083e9e0516d8c -reec680fe322aea5d1ecf8fdf1f14a273afdf6c53
--- Application/Ringtoets/src/Application.Ringtoets.Storage/Read/GrassCoverErosionInwards/GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions.cs	(.../GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions.cs)	(revision 8cb270db5fbcb82f19d6f3a390f083e9e0516d8c)
+++ Application/Ringtoets/src/Application.Ringtoets.Storage/Read/GrassCoverErosionInwards/GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions.cs	(.../GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions.cs)	(revision eec680fe322aea5d1ecf8fdf1f14a273afdf6c53)
@@ -19,25 +19,35 @@
 // Stichting Deltares and remain full property of Stichting Deltares at all times.
 // All rights reserved.
 
+using System;
 using Application.Ringtoets.Storage.DbContext;
 using Ringtoets.Common.Data.Hydraulics;
 using Ringtoets.GrassCoverErosionInwards.Data;
 
 namespace Application.Ringtoets.Storage.Read.GrassCoverErosionInwards
 {
     /// <summary>
-    /// Extension methods for <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/> related to creating 
-    /// a <see cref="SubCalculationAssessmentOutput"/>.
+    /// Extension methods for <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/>
+    /// related to creating a <see cref="SubCalculationAssessmentOutput"/>.
     /// </summary>
     internal static class GrassCoverErosionInwardsDikeHeightOutputEntityReadExtensions
     {
         /// <summary>
-        /// Reads the <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/> and use the information to construct a <see cref="SubCalculationAssessmentOutput"/>.
+        /// Reads the <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/> and use
+        /// the information to construct a <see cref="SubCalculationAssessmentOutput"/>.
         /// </summary>
-        /// <param name="entity">The <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/> to create <see cref="SubCalculationAssessmentOutput"/> for.</param>
+        /// <param name="entity">The <see cref="GrassCoverErosionInwardsDikeHeightOutputEntity"/>
+        /// to create <see cref="SubCalculationAssessmentOutput"/> for.</param>
         /// <returns>A new <see cref="SubCalculationAssessmentOutput"/>.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="entity"/>
+        /// is <c>null</c>.</exception>
         internal static SubCalculationAssessmentOutput Read(this GrassCoverErosionInwardsDikeHeightOutputEntity entity)
         {
+            if (entity == null)
+            {
+                throw new ArgumentNullException(nameof(entity));
+            }
+
             return new SubCalculationAssessmentOutput(entity.DikeHeight.ToNullAsNaN(),
                                                   entity.TargetProbability.ToNullAsNaN(),
                                                   entity.TargetReliability.ToNullAsNaN(),