Index: Ringtoets/Common/src/Ringtoets.Common.Data/UpdateDataStrategies/UpdateDataStrategyBase.cs
===================================================================
diff -u -rfe48b787571cbc5b0fa82df6c9bb718fbd869f04 -rc0af7b97084a578a78834cbccb43bf53ca39b8e6
--- Ringtoets/Common/src/Ringtoets.Common.Data/UpdateDataStrategies/UpdateDataStrategyBase.cs	(.../UpdateDataStrategyBase.cs)	(revision fe48b787571cbc5b0fa82df6c9bb718fbd869f04)
+++ Ringtoets/Common/src/Ringtoets.Common.Data/UpdateDataStrategies/UpdateDataStrategyBase.cs	(.../UpdateDataStrategyBase.cs)	(revision c0af7b97084a578a78834cbccb43bf53ca39b8e6)
@@ -46,19 +46,14 @@
     {
         protected readonly TFailureMechanism FailureMechanism;
         private readonly IEqualityComparer<TTargetData> equalityComparer;
-        private ObservableUniqueItemCollectionWithSourcePath<TTargetData> targetCollection;
 
         /// <summary>
         /// Creates a new instance of <see cref="UpdateDataStrategyBase{TTargetData,TFailureMechanism}"/> object.
         /// </summary>
         /// <param name="failureMechanism">The failure mechanism which needs to be updated.</param>
-        /// <param name="targetCollection">The collection to add the updated objects to.</param>
         /// <param name="equalityComparer">The comparer which should be used to determine when two objects are equal.</param>
         /// <exception cref="ArgumentNullException">Thrown when any input parameter is <c>null</c>.</exception>
-        protected UpdateDataStrategyBase(
-            TFailureMechanism failureMechanism,
-            ObservableUniqueItemCollectionWithSourcePath<TTargetData> targetCollection,
-            IEqualityComparer<TTargetData> equalityComparer)
+        protected UpdateDataStrategyBase(TFailureMechanism failureMechanism, IEqualityComparer<TTargetData> equalityComparer)
         {
             if (failureMechanism == null)
             {
@@ -68,13 +63,8 @@
             {
                 throw new ArgumentNullException(nameof(equalityComparer));
             }
-            if (targetCollection == null)
-            {
-                throw new ArgumentNullException(nameof(targetCollection));
-            }
 
             this.equalityComparer = equalityComparer;
-            this.targetCollection = targetCollection;
             FailureMechanism = failureMechanism;
         }
 
@@ -99,16 +89,22 @@
         /// Updates the items and their associated data within the target collection with the data contained 
         /// in the imported data collection.
         /// </summary>
+        /// <param name="targetDataCollection">The target collection that needs to be updated.</param>
         /// <param name="importedDataCollection">The imported data collection that is used to update
-        /// the <see cref="targetCollection"/>.</param>
+        /// the <paramref name="targetDataCollection"/>.</param>
         /// <param name="sourceFilePath">The source file path.</param>
         /// <returns>A <see cref="IEnumerable{T}"/> of affected objects.</returns>
         /// <exception cref="UpdateDataException">Thrown when an error occurred while updating the data.</exception>
         /// <exception cref="ArgumentException">Thrown when <paramref name="importedDataCollection"/> contains 
         /// <c>null</c> elements.</exception>
-        protected IEnumerable<IObservable> UpdateTargetCollectionData(IEnumerable<TTargetData> importedDataCollection,
+        protected IEnumerable<IObservable> UpdateTargetCollectionData(ObservableUniqueItemCollectionWithSourcePath<TTargetData> targetDataCollection,
+                                                                      IEnumerable<TTargetData> importedDataCollection,
                                                                       string sourceFilePath)
         {
+            if (targetDataCollection == null)
+            {
+                throw new ArgumentNullException(nameof(targetDataCollection));
+            }
             if (importedDataCollection == null)
             {
                 throw new ArgumentNullException(nameof(importedDataCollection));
@@ -117,44 +113,47 @@
             {
                 throw new ArgumentNullException(nameof(sourceFilePath));
             }
-            return ModifyDataCollection(importedDataCollection, sourceFilePath);
+
+            return ModifyDataCollection(targetDataCollection, importedDataCollection, sourceFilePath);
         }
 
         /// <summary>
         /// Identifies which items were changed, removed and added to the target collection 
         /// when compared with the imported data and performs the necessary operations for 
         /// the dependent data of the affected elements. 
         /// </summary>
+        /// <param name="targetDataCollection">The target data collection which needs to be updated.</param>
         /// <param name="importedDataCollection">The imported data collection which is used to update 
-        /// the <see cref="targetCollection"/>.</param>
+        /// the <paramref name="targetDataCollection"/>.</param>
         /// <param name="sourceFilePath">The source file path.</param>
         /// <returns>A <see cref="IEnumerable{T}"/> with affected objects.</returns>
         /// <exception cref="UpdateDataException">Thrown when:
         /// <list type="bullet">
-        /// <item>duplicate items are being added to the <see cref="targetCollection"/>.</item>
+        /// <item>duplicate items are being added to the <paramref name="targetDataCollection"/>.</item>
         /// <item>duplicate items are found in the <paramref name="importedDataCollection"/>.</item>
         /// </list>
         /// </exception>
-        /// <exception cref="ArgumentNullException">Thrown when <paramref name="importedDataCollection"/>
-        /// is <c>null</c>.</exception>
+        /// <exception cref="ArgumentNullException">Thrown when either <paramref name="targetDataCollection"/> 
+        /// or <paramref name="importedDataCollection"/> is <c>null</c>.</exception>
         /// <exception cref="ArgumentException">Thrown when <paramref name="importedDataCollection"/> contains 
         /// <c>null</c> elements.</exception>
-        private IEnumerable<IObservable> ModifyDataCollection(IEnumerable<TTargetData> importedDataCollection,
+        private IEnumerable<IObservable> ModifyDataCollection(ObservableUniqueItemCollectionWithSourcePath<TTargetData> targetDataCollection,
+                                                              IEnumerable<TTargetData> importedDataCollection,
                                                               string sourceFilePath)
         {
             TTargetData[] importedObjects = importedDataCollection.ToArray();
 
-            var modification = new CollectionModification(targetCollection, importedObjects, equalityComparer);
+            var modification = new CollectionModification(targetDataCollection, importedObjects, equalityComparer);
 
             var affectedObjects = new List<IObservable>();
             if (modification.HasUpdates())
             {
-                affectedObjects.Add(targetCollection);
+                affectedObjects.Add(targetDataCollection);
             }
             affectedObjects.AddRange(UpdateData(modification.ObjectsToBeUpdated.Values, importedObjects));
             affectedObjects.AddRange(RemoveData(modification.ObjectsToBeRemoved));
-            targetCollection.Clear();
-            targetCollection.AddRange(modification.GetModifiedCollection(), sourceFilePath);
+            targetDataCollection.Clear();
+            targetDataCollection.AddRange(modification.GetModifiedCollection(), sourceFilePath);
 
             return affectedObjects.Distinct(new ReferenceEqualityComparer<IObservable>());
         }