Index: Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Forms/PropertyClasses/HeightStructuresFailureMechanismProperties.cs
===================================================================
diff -u -r6ac1d016e76120e778964de3ad7e2c0d6c837669 -r16d53fca2e51dcd5ede08bbebcda854c783ab025
--- Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Forms/PropertyClasses/HeightStructuresFailureMechanismProperties.cs	(.../HeightStructuresFailureMechanismProperties.cs)	(revision 6ac1d016e76120e778964de3ad7e2c0d6c837669)
+++ Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Forms/PropertyClasses/HeightStructuresFailureMechanismProperties.cs	(.../HeightStructuresFailureMechanismProperties.cs)	(revision 16d53fca2e51dcd5ede08bbebcda854c783ab025)
@@ -87,12 +87,8 @@
             }
             set
             {
-                IEnumerable<IObservable> affectedObjects = propertyChangeHandler.SetPropertyValueAfterConfirmation(
-                    data,
-                    value,
-                    (f, v) => f.GeneralInput.N = v);
-
-                NotifyAffectedObjects(affectedObjects);
+                data.GeneralInput.N = value;
+                data.NotifyObservers();
             }
         }
 
@@ -101,22 +97,9 @@
         [DynamicVisibleValidationMethod]
         public bool DynamicVisibleValidationMethod(string propertyName)
         {
-            if (!data.IsRelevant && ShouldHidePropertyWhenFailureMechanismIrrelevant(propertyName))
-            {
-                return false;
-            }
-
-            return true;
+            return data.IsRelevant || !ShouldHidePropertyWhenFailureMechanismIrrelevant(propertyName);
         }
 
-        private static void NotifyAffectedObjects(IEnumerable<IObservable> affectedObjects)
-        {
-            foreach (IObservable affectedObject in affectedObjects)
-            {
-                affectedObject.NotifyObservers();
-            }
-        }
-
         private bool ShouldHidePropertyWhenFailureMechanismIrrelevant(string propertyName)
         {
             return nameof(N).Equals(propertyName)
Index: Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Forms.Test/PropertyClasses/HeightStructuresFailureMechanismPropertiesTest.cs
===================================================================
diff -u -r65ce8c5ab171b234e33e2291998c9d89276db896 -r16d53fca2e51dcd5ede08bbebcda854c783ab025
--- Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Forms.Test/PropertyClasses/HeightStructuresFailureMechanismPropertiesTest.cs	(.../HeightStructuresFailureMechanismPropertiesTest.cs)	(revision 65ce8c5ab171b234e33e2291998c9d89276db896)
+++ Ringtoets/HeightStructures/test/Ringtoets.HeightStructures.Forms.Test/PropertyClasses/HeightStructuresFailureMechanismPropertiesTest.cs	(.../HeightStructuresFailureMechanismPropertiesTest.cs)	(revision 16d53fca2e51dcd5ede08bbebcda854c783ab025)
@@ -246,18 +246,16 @@
         {
             // Setup
             var mockRepository = new MockRepository();
-            var observable = mockRepository.StrictMock<IObservable>();
+            var observer = mockRepository.StrictMock<IObserver>();
             mockRepository.ReplayAll();
 
             var failureMechanism = new HeightStructuresFailureMechanism();
+            failureMechanism.Attach(observer);
 
             var changeHandler = new FailureMechanismSetPropertyValueAfterConfirmationParameterTester<HeightStructuresFailureMechanism, double>(
                 failureMechanism,
                 value,
-                new[]
-                {
-                    observable
-                });
+                new IObservable[0]);
 
             var properties = new HeightStructuresFailureMechanismProperties(failureMechanism, changeHandler);
 
@@ -267,7 +265,6 @@
             // Assert
             const string expectedMessage = "De waarde voor 'N' moet in het bereik [1,00, 20,00] liggen.";
             TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentOutOfRangeException>(test, expectedMessage);
-            Assert.IsTrue(changeHandler.Called);
             mockRepository.VerifyAll();
         }
 
@@ -279,19 +276,16 @@
         {
             // Setup
             var mockRepository = new MockRepository();
-            var observable = mockRepository.StrictMock<IObservable>();
-            observable.Expect(o => o.NotifyObservers());
-
+            var observer = mockRepository.StrictMock<IObserver>();
+            observer.Expect(o => o.UpdateObserver());
             mockRepository.ReplayAll();
 
             var failureMechanism = new HeightStructuresFailureMechanism();
+            failureMechanism.Attach(observer);
             var changeHandler = new FailureMechanismSetPropertyValueAfterConfirmationParameterTester<HeightStructuresFailureMechanism, double>(
                 failureMechanism,
                 value,
-                new[]
-                {
-                    observable
-                });
+                new IObservable[0]);
 
             var properties = new HeightStructuresFailureMechanismProperties(failureMechanism, changeHandler);
 
@@ -300,7 +294,6 @@
 
             // Assert
             Assert.AreEqual(value, failureMechanism.GeneralInput.N, failureMechanism.GeneralInput.N.GetAccuracy());
-            Assert.IsTrue(changeHandler.Called);
             mockRepository.VerifyAll();
         }