diff --git a/Applications/Quickstarts.Servers/SampleNodeManager/SampleNodeManager.cs b/Applications/Quickstarts.Servers/SampleNodeManager/SampleNodeManager.cs
index 3b94e5d02..9b495ab6b 100644
--- a/Applications/Quickstarts.Servers/SampleNodeManager/SampleNodeManager.cs
+++ b/Applications/Quickstarts.Servers/SampleNodeManager/SampleNodeManager.cs
@@ -506,7 +506,7 @@ protected virtual void AddPredefinedNode(ISystemContext context, NodeState node)
                 LocalReference referenceToRemove = new LocalReference(
                     (NodeId)reference.TargetId,
                     reference.ReferenceTypeId,
-                    reference.IsInverse,
+                    !reference.IsInverse,
                     node.NodeId);
 
                 referencesToRemove.Add(referenceToRemove);
diff --git a/Libraries/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs b/Libraries/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs
index 405a9d174..ea75e4134 100644
--- a/Libraries/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs
+++ b/Libraries/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs
@@ -705,7 +705,7 @@ protected virtual void AddPredefinedNode(ISystemContext context, NodeState node)
                 LocalReference referenceToRemove = new LocalReference(
                     (NodeId)reference.TargetId,
                     reference.ReferenceTypeId,
-                    reference.IsInverse,
+                    !reference.IsInverse,
                     node.NodeId);
 
                 referencesToRemove.Add(referenceToRemove);
diff --git a/Libraries/Opc.Ua.Server/NodeManager/MasterNodeManager.cs b/Libraries/Opc.Ua.Server/NodeManager/MasterNodeManager.cs
index b2f3f442a..28ec4b5f0 100644
--- a/Libraries/Opc.Ua.Server/NodeManager/MasterNodeManager.cs
+++ b/Libraries/Opc.Ua.Server/NodeManager/MasterNodeManager.cs
@@ -657,8 +657,7 @@ public void RemoveReferences(List<LocalReference> referencesToRemove)
                 LocalReference reference = referencesToRemove[ii];
 
                 // find source node.
-                INodeManager nodeManager = null;
-                object sourceHandle = GetManagerHandle(reference.SourceId, out nodeManager);
+                object sourceHandle = GetManagerHandle(reference.SourceId, out INodeManager nodeManager);
 
                 if (sourceHandle == null)
                 {
diff --git a/Stack/Opc.Ua.Core/Stack/State/NodeState.cs b/Stack/Opc.Ua.Core/Stack/State/NodeState.cs
index f35cf297b..a0c0a5220 100644
--- a/Stack/Opc.Ua.Core/Stack/State/NodeState.cs
+++ b/Stack/Opc.Ua.Core/Stack/State/NodeState.cs
@@ -2347,10 +2347,7 @@ public void SetAreEventsMonitored(ISystemContext context, bool areEventsMonitore
         /// <param name="e">The event to report.</param>
         public virtual void ReportEvent(ISystemContext context, IFilterTarget e)
         {
-            if (OnReportEvent != null)
-            {
-                OnReportEvent(context, this, e);
-            }
+            OnReportEvent?.Invoke(context, this, e);
 
             // report event to notifier sources.
             if (m_notifiers != null)
@@ -2498,10 +2495,7 @@ public virtual void RemoveNotifier(ISystemContext context, NodeState target, boo
         /// <param name="includeChildren">Whether to recursively report events for the children.</param>
         public virtual void ConditionRefresh(ISystemContext context, List<IFilterTarget> events, bool includeChildren)
         {
-            if (OnConditionRefresh != null)
-            {
-                OnConditionRefresh(context, this, events);
-            }
+            OnConditionRefresh?.Invoke(context, this, events);
 
             if (includeChildren)
             {
@@ -2581,15 +2575,9 @@ public void ClearChangeMasks(ISystemContext context, bool includeChildren)
 
             if (m_changeMasks != NodeStateChangeMasks.None)
             {
-                if (OnStateChanged != null)
-                {
-                    OnStateChanged(context, this, m_changeMasks);
-                }
+                OnStateChanged?.Invoke(context, this, m_changeMasks);
 
-                if (StateChanged != null)
-                {
-                    StateChanged(context, this, m_changeMasks);
-                }
+                StateChanged?.Invoke(context, this, m_changeMasks);
 
                 m_changeMasks = NodeStateChangeMasks.None;
             }
@@ -2912,10 +2900,7 @@ public virtual bool Validate(ISystemContext context)
 
             PopulateBrowser(context, browser);
 
-            if (OnPopulateBrowser != null)
-            {
-                OnPopulateBrowser(context, this, browser);
-            }
+            OnPopulateBrowser?.Invoke(context, this, browser);
 
             return browser;
         }
@@ -4472,25 +4457,11 @@ public void RemoveChild(BaseInstanceState child)
                 return false;
             }
 
-            NodeStateReference sourceRef = null;
-
-            foreach (var m_refKey in m_references.Keys)
+            if (m_references.Remove(new NodeStateReference(referenceTypeId, isInverse, targetId)))
             {
-                if (m_refKey.TargetId != null && m_refKey.TargetId.IdentifierText.Equals(targetId.IdentifierText))
-                {
-                    sourceRef = m_refKey as NodeStateReference;
-                    break;
-                }
-            }
-
-            if (sourceRef != null)
-            {
-                if (m_references.Remove(sourceRef))
-                {
-                    m_changeMasks |= NodeStateChangeMasks.References;
-                    OnReferenceRemoved?.Invoke(this, referenceTypeId, isInverse, targetId);
-                    return true;
-                }
+                m_changeMasks |= NodeStateChangeMasks.References;
+                OnReferenceRemoved?.Invoke(this, referenceTypeId, isInverse, targetId);
+                return true;
             }
 
             return false;