Inheritance: UAInstance
        /// <summary>
        /// Adds a node to the set.
        /// </summary>
        public void Export(ISystemContext context, NodeState node, bool outputRedundantNames = true)
        {
            if (node == null)
            {
                throw new ArgumentNullException(nameof(node));
            }

            if (Opc.Ua.NodeId.IsNull(node.NodeId))
            {
                throw new ArgumentException("A non-null NodeId must be specified.");
            }

            UANode exportedNode = null;

            switch (node.NodeClass)
            {
            case NodeClass.Object:
            {
                BaseObjectState o     = (BaseObjectState)node;
                UAObject        value = new UAObject();
                value.EventNotifier = o.EventNotifier;

                if (o.Parent != null)
                {
                    value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                }

                exportedNode = value;
                break;
            }

            case NodeClass.Variable:
            {
                BaseVariableState o     = (BaseVariableState)node;
                UAVariable        value = new UAVariable();
                value.DataType                = ExportAlias(o.DataType, context.NamespaceUris);
                value.ValueRank               = o.ValueRank;
                value.ArrayDimensions         = Export(o.ArrayDimensions);
                value.AccessLevel             = o.AccessLevelEx;
                value.MinimumSamplingInterval = o.MinimumSamplingInterval;
                value.Historizing             = o.Historizing;

                if (o.Parent != null)
                {
                    value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                }

                if (o.Value != null)
                {
                    XmlEncoder encoder = CreateEncoder(context);

                    Variant variant = new Variant(o.Value);
                    encoder.WriteVariantContents(variant.Value, variant.TypeInfo);

                    XmlDocument document = new XmlDocument();
                    document.InnerXml = encoder.Close();
                    value.Value       = document.DocumentElement;
                }

                exportedNode = value;
                break;
            }

            case NodeClass.Method:
            {
                MethodState o     = (MethodState)node;
                UAMethod    value = new UAMethod();
                value.Executable = o.Executable;

                if (o.TypeDefinitionId != null && !o.TypeDefinitionId.IsNullNodeId && o.TypeDefinitionId != o.NodeId)
                {
                    value.MethodDeclarationId = Export(o.TypeDefinitionId, context.NamespaceUris);
                }

                if (o.Parent != null)
                {
                    value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                }

                exportedNode = value;
                break;
            }

            case NodeClass.View:
            {
                ViewState o     = (ViewState)node;
                UAView    value = new UAView();
                value.ContainsNoLoops = o.ContainsNoLoops;
                exportedNode          = value;
                break;
            }

            case NodeClass.ObjectType:
            {
                BaseObjectTypeState o     = (BaseObjectTypeState)node;
                UAObjectType        value = new UAObjectType();
                value.IsAbstract = o.IsAbstract;
                exportedNode     = value;
                break;
            }

            case NodeClass.VariableType:
            {
                BaseVariableTypeState o     = (BaseVariableTypeState)node;
                UAVariableType        value = new UAVariableType();
                value.IsAbstract      = o.IsAbstract;
                value.DataType        = ExportAlias(o.DataType, context.NamespaceUris);
                value.ValueRank       = o.ValueRank;
                value.ArrayDimensions = Export(o.ArrayDimensions);

                if (o.Value != null)
                {
                    XmlEncoder encoder = CreateEncoder(context);

                    Variant variant = new Variant(o.Value);
                    encoder.WriteVariantContents(variant.Value, variant.TypeInfo);

                    XmlDocument document = new XmlDocument();
                    document.InnerXml = encoder.Close();
                    value.Value       = document.DocumentElement;
                }

                exportedNode = value;
                break;
            }

            case NodeClass.DataType:
            {
                DataTypeState o     = (DataTypeState)node;
                UADataType    value = new UADataType();
                value.IsAbstract = o.IsAbstract;
                value.Definition = Export(o, o.DataTypeDefinition, context.NamespaceUris, outputRedundantNames);
                value.Purpose    = o.Purpose;
                exportedNode     = value;
                break;
            }

            case NodeClass.ReferenceType:
            {
                ReferenceTypeState o     = (ReferenceTypeState)node;
                UAReferenceType    value = new UAReferenceType();
                value.IsAbstract = o.IsAbstract;

                if (!Opc.Ua.LocalizedText.IsNullOrEmpty(o.InverseName))
                {
                    value.InverseName = Export(new Opc.Ua.LocalizedText[] { o.InverseName });
                }

                value.Symmetric = o.Symmetric;
                exportedNode    = value;
                break;
            }
            }

            exportedNode.NodeId     = Export(node.NodeId, context.NamespaceUris);
            exportedNode.BrowseName = Export(node.BrowseName, context.NamespaceUris);

            if (outputRedundantNames || node.DisplayName.Text != node.BrowseName.Name)
            {
                exportedNode.DisplayName = Export(new Opc.Ua.LocalizedText[] { node.DisplayName });
            }
            else
            {
                exportedNode.DisplayName = null;
            }

            if (node.Description != null && !String.IsNullOrEmpty(node.Description.Text))
            {
                exportedNode.Description = Export(new Opc.Ua.LocalizedText[] { node.Description });
            }
            else
            {
                exportedNode.Description = new LocalizedText[0];
            }

            exportedNode.Category      = (node.Categories != null && node.Categories.Count > 0) ? new List <string>(node.Categories).ToArray() : null;
            exportedNode.ReleaseStatus = node.ReleaseStatus;
            exportedNode.WriteMask     = (uint)node.WriteMask;
            exportedNode.UserWriteMask = (uint)node.UserWriteMask;
            exportedNode.Extensions    = node.Extensions;

            if (!String.IsNullOrEmpty(node.SymbolicName) && node.SymbolicName != node.BrowseName.Name)
            {
                exportedNode.SymbolicName = node.SymbolicName;
            }

            // export references.
            INodeBrowser     browser            = node.CreateBrowser(context, null, null, true, BrowseDirection.Both, null, null, true);
            List <Reference> exportedReferences = new List <Reference>();
            IReference       reference          = browser.Next();

            while (reference != null)
            {
                if (node.NodeClass == NodeClass.Method)
                {
                    if (!reference.IsInverse && reference.ReferenceTypeId == ReferenceTypeIds.HasTypeDefinition)
                    {
                        reference = browser.Next();
                        continue;
                    }
                }

                Reference exportedReference = new Reference();

                exportedReference.ReferenceType = ExportAlias(reference.ReferenceTypeId, context.NamespaceUris);
                exportedReference.IsForward     = !reference.IsInverse;
                exportedReference.Value         = Export(reference.TargetId, context.NamespaceUris, context.ServerUris);
                exportedReferences.Add(exportedReference);

                reference = browser.Next();
            }

            exportedNode.References = exportedReferences.ToArray();

            // add node to list.
            UANode[] nodes = null;

            int count = 1;

            if (this.Items == null)
            {
                nodes = new UANode[count];
            }
            else
            {
                count += this.Items.Length;
                nodes  = new UANode[count];
                Array.Copy(this.Items, nodes, this.Items.Length);
            }

            nodes[count - 1] = exportedNode;

            this.Items = nodes;

            // recusively process children.
            List <BaseInstanceState> children = new List <BaseInstanceState>();

            node.GetChildren(context, children);

            for (int ii = 0; ii < children.Count; ii++)
            {
                Export(context, children[ii], outputRedundantNames);
            }
        }
        /// <summary>
        /// Imports a node from the set.
        /// </summary>
        private NodeState Import(ISystemContext context, UANode node)
        {
            NodeState importedNode = null;

            NodeClass nodeClass = NodeClass.Unspecified;

            if (node is UAObject)
            {
                nodeClass = NodeClass.Object;
            }
            else if (node is UAVariable)
            {
                nodeClass = NodeClass.Variable;
            }
            else if (node is UAMethod)
            {
                nodeClass = NodeClass.Method;
            }
            else if (node is UAObjectType)
            {
                nodeClass = NodeClass.ObjectType;
            }
            else if (node is UAVariableType)
            {
                nodeClass = NodeClass.VariableType;
            }
            else if (node is UADataType)
            {
                nodeClass = NodeClass.DataType;
            }
            else if (node is UAReferenceType)
            {
                nodeClass = NodeClass.ReferenceType;
            }
            else if (node is UAView)
            {
                nodeClass = NodeClass.View;
            }

            switch (nodeClass)
            {
            case NodeClass.Object:
            {
                UAObject        o     = (UAObject)node;
                BaseObjectState value = new BaseObjectState(null);
                value.EventNotifier = o.EventNotifier;
                importedNode        = value;
                break;
            }

            case NodeClass.Variable:
            {
                UAVariable o = (UAVariable)node;

                NodeId typeDefinitionId = null;

                if (node.References != null)
                {
                    for (int ii = 0; ii < node.References.Length; ii++)
                    {
                        Opc.Ua.NodeId         referenceTypeId = ImportNodeId(node.References[ii].ReferenceType, context.NamespaceUris, true);
                        bool                  isInverse       = !node.References[ii].IsForward;
                        Opc.Ua.ExpandedNodeId targetId        = ImportExpandedNodeId(node.References[ii].Value, context.NamespaceUris, context.ServerUris);

                        if (referenceTypeId == ReferenceTypeIds.HasTypeDefinition && !isInverse)
                        {
                            typeDefinitionId = Opc.Ua.ExpandedNodeId.ToNodeId(targetId, context.NamespaceUris);
                            break;
                        }
                    }
                }

                BaseVariableState value = null;

                if (typeDefinitionId == Opc.Ua.VariableTypeIds.PropertyType)
                {
                    value = new PropertyState(null);
                }
                else
                {
                    value = new BaseDataVariableState(null);
                }

                value.DataType                = ImportNodeId(o.DataType, context.NamespaceUris, true);
                value.ValueRank               = o.ValueRank;
                value.ArrayDimensions         = ImportArrayDimensions(o.ArrayDimensions);
                value.AccessLevelEx           = o.AccessLevel;
                value.UserAccessLevel         = (byte)(o.AccessLevel & 0xFF);
                value.MinimumSamplingInterval = o.MinimumSamplingInterval;
                value.Historizing             = o.Historizing;

                if (o.Value != null)
                {
                    XmlDecoder decoder  = CreateDecoder(context, o.Value);
                    TypeInfo   typeInfo = null;
                    value.Value = decoder.ReadVariantContents(out typeInfo);
                    decoder.Close();
                }

                importedNode = value;
                break;
            }

            case NodeClass.Method:
            {
                UAMethod    o     = (UAMethod)node;
                MethodState value = new MethodState(null);
                value.Executable       = o.Executable;
                value.UserExecutable   = o.Executable;
                value.TypeDefinitionId = ImportNodeId(o.MethodDeclarationId, context.NamespaceUris, true);
                importedNode           = value;
                break;
            }

            case NodeClass.View:
            {
                UAView    o     = (UAView)node;
                ViewState value = new ViewState();
                value.ContainsNoLoops = o.ContainsNoLoops;
                importedNode          = value;
                break;
            }

            case NodeClass.ObjectType:
            {
                UAObjectType        o     = (UAObjectType)node;
                BaseObjectTypeState value = new BaseObjectTypeState();
                value.IsAbstract = o.IsAbstract;
                importedNode     = value;
                break;
            }

            case NodeClass.VariableType:
            {
                UAVariableType        o     = (UAVariableType)node;
                BaseVariableTypeState value = new BaseDataVariableTypeState();
                value.IsAbstract      = o.IsAbstract;
                value.DataType        = ImportNodeId(o.DataType, context.NamespaceUris, true);
                value.ValueRank       = o.ValueRank;
                value.ArrayDimensions = ImportArrayDimensions(o.ArrayDimensions);

                if (o.Value != null)
                {
                    XmlDecoder decoder  = CreateDecoder(context, o.Value);
                    TypeInfo   typeInfo = null;
                    value.Value = decoder.ReadVariantContents(out typeInfo);
                    decoder.Close();
                }

                importedNode = value;
                break;
            }

            case NodeClass.DataType:
            {
                UADataType    o     = (UADataType)node;
                DataTypeState value = new DataTypeState();
                value.IsAbstract = o.IsAbstract;
                Opc.Ua.DataTypeDefinition dataTypeDefinition = Import(o, o.Definition, context.NamespaceUris);
                value.DataTypeDefinition = new ExtensionObject(dataTypeDefinition);
                value.Purpose            = o.Purpose;
                value.DataTypeModifier   = DataTypeModifier.None;

                if (o.Definition != null)
                {
                    if (o.Definition.IsOptionSet)
                    {
                        value.DataTypeModifier = DataTypeModifier.OptionSet;
                    }
                    else if (o.Definition.IsUnion)
                    {
                        value.DataTypeModifier = DataTypeModifier.Union;
                    }
                }

                importedNode = value;
                break;
            }

            case NodeClass.ReferenceType:
            {
                UAReferenceType    o     = (UAReferenceType)node;
                ReferenceTypeState value = new ReferenceTypeState();
                value.IsAbstract  = o.IsAbstract;
                value.InverseName = Import(o.InverseName);
                value.Symmetric   = o.Symmetric;
                importedNode      = value;
                break;
            }
            }

            importedNode.NodeId      = ImportNodeId(node.NodeId, context.NamespaceUris, false);
            importedNode.BrowseName  = ImportQualifiedName(node.BrowseName, context.NamespaceUris);
            importedNode.DisplayName = Import(node.DisplayName);

            if (importedNode.DisplayName == null)
            {
                importedNode.DisplayName = new Ua.LocalizedText(importedNode.BrowseName.Name);
            }

            importedNode.Description   = Import(node.Description);
            importedNode.Categories    = (node.Category != null && node.Category.Length > 0) ? node.Category : null;
            importedNode.ReleaseStatus = node.ReleaseStatus;
            importedNode.WriteMask     = (AttributeWriteMask)node.WriteMask;
            importedNode.UserWriteMask = (AttributeWriteMask)node.UserWriteMask;
            importedNode.Extensions    = node.Extensions;

            if (!String.IsNullOrEmpty(node.SymbolicName))
            {
                importedNode.SymbolicName = node.SymbolicName;
            }

            if (node.References != null)
            {
                BaseInstanceState instance = importedNode as BaseInstanceState;
                BaseTypeState     type     = importedNode as BaseTypeState;

                for (int ii = 0; ii < node.References.Length; ii++)
                {
                    Opc.Ua.NodeId         referenceTypeId = ImportNodeId(node.References[ii].ReferenceType, context.NamespaceUris, true);
                    bool                  isInverse       = !node.References[ii].IsForward;
                    Opc.Ua.ExpandedNodeId targetId        = ImportExpandedNodeId(node.References[ii].Value, context.NamespaceUris, context.ServerUris);

                    if (instance != null)
                    {
                        if (referenceTypeId == ReferenceTypeIds.HasModellingRule && !isInverse)
                        {
                            instance.ModellingRuleId = Opc.Ua.ExpandedNodeId.ToNodeId(targetId, context.NamespaceUris);
                            continue;
                        }

                        if (referenceTypeId == ReferenceTypeIds.HasTypeDefinition && !isInverse)
                        {
                            instance.TypeDefinitionId = Opc.Ua.ExpandedNodeId.ToNodeId(targetId, context.NamespaceUris);
                            continue;
                        }
                    }

                    if (type != null)
                    {
                        if (referenceTypeId == ReferenceTypeIds.HasSubtype && isInverse)
                        {
                            type.SuperTypeId = Opc.Ua.ExpandedNodeId.ToNodeId(targetId, context.NamespaceUris);
                            continue;
                        }
                    }

                    importedNode.AddReference(referenceTypeId, isInverse, targetId);
                }
            }

            return(importedNode);
        }
        /// <summary>
        /// Adds a node to the set.
        /// </summary>
        public void Export(ISystemContext context, NodeState node)
        {
            if (node == null) throw new ArgumentNullException("node");

            if (Opc.Ua.NodeId.IsNull(node.NodeId))
            {
                throw new ArgumentException("A non-null NodeId must be specified.");
            }

            UANode exportedNode = null;

            switch (node.NodeClass)
            {
                case NodeClass.Object:
                {
                    BaseObjectState o = (BaseObjectState)node;
                    UAObject value = new UAObject();
                    value.EventNotifier = o.EventNotifier;

                    if (o.Parent != null)
                    {
                        value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                    }

                    exportedNode = value;
                    break;
                }

                case NodeClass.Variable:
                {
                    BaseVariableState o = (BaseVariableState)node;
                    UAVariable value = new UAVariable();
                    value.DataType = ExportAlias(o.DataType, context.NamespaceUris);
                    value.ValueRank = o.ValueRank;
                    value.ArrayDimensions = Export(o.ArrayDimensions);
                    value.AccessLevel = o.AccessLevel;
                    value.UserAccessLevel = o.UserAccessLevel;
                    value.MinimumSamplingInterval = o.MinimumSamplingInterval;
                    value.Historizing = o.Historizing;

                    if (o.Parent != null)
                    {
                        value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                    }

                    if (o.Value != null)
                    {
                        XmlEncoder encoder = CreateEncoder(context);

                        Variant variant = new Variant(o.Value);
                        encoder.WriteVariantContents(variant.Value, variant.TypeInfo);

                        XmlDocument document = new XmlDocument();
                        document.InnerXml = encoder.Close();
                        value.Value = document.DocumentElement;
                    }

                    exportedNode = value;                 
                    break;
                }

                case NodeClass.Method:
                {
                    MethodState o = (MethodState)node;
                    UAMethod value = new UAMethod();
                    value.Executable = o.Executable;
                    value.UserExecutable = o.UserExecutable;

                    if (o.Parent != null)
                    {
                        value.ParentNodeId = ExportAlias(o.Parent.NodeId, context.NamespaceUris);
                    }

                    exportedNode = value;
                    break;
                }

                case NodeClass.View:
                {
                    ViewState o = (ViewState)node;
                    UAView value = new UAView();
                    value.ContainsNoLoops = o.ContainsNoLoops;
                    exportedNode = value;
                    break;
                }

                case NodeClass.ObjectType:
                {
                    BaseObjectTypeState o = (BaseObjectTypeState)node;
                    UAObjectType value = new UAObjectType();
                    value.IsAbstract = o.IsAbstract;
                    exportedNode = value;
                    break;
                }

                case NodeClass.VariableType:
                {
                    BaseVariableTypeState o = (BaseVariableTypeState)node;
                    UAVariableType value = new UAVariableType();
                    value.IsAbstract = o.IsAbstract;
                    value.DataType = ExportAlias(o.DataType, context.NamespaceUris);
                    value.ValueRank = o.ValueRank;
                    value.ArrayDimensions = Export(o.ArrayDimensions);

                    if (o.Value != null)
                    {
                        XmlEncoder encoder = CreateEncoder(context);

                        Variant variant = new Variant(o.Value);
                        encoder.WriteVariantContents(variant.Value, variant.TypeInfo);

                        XmlDocument document = new XmlDocument();
                        document.InnerXml = encoder.Close();
                        value.Value = document.DocumentElement;
                    }

                    exportedNode = value;
                    break;
                }

                case NodeClass.DataType:
                {
                    DataTypeState o = (DataTypeState)node;
                    UADataType value = new UADataType();
                    value.IsAbstract = o.IsAbstract;
                    value.Definition = Export(o.Definition, context.NamespaceUris);
                    exportedNode = value;
                    break;
                }

                case NodeClass.ReferenceType:
                {
                    ReferenceTypeState o = (ReferenceTypeState)node;
                    UAReferenceType value = new UAReferenceType();
                    value.IsAbstract = o.IsAbstract;
                    value.InverseName = Export(new Opc.Ua.LocalizedText[] { o.InverseName });
                    value.Symmetric = o.Symmetric;
                    exportedNode = value;
                    break;
                }
            }

            exportedNode.NodeId = Export(node.NodeId, context.NamespaceUris);
            exportedNode.BrowseName = Export(node.BrowseName, context.NamespaceUris);
            exportedNode.DisplayName = Export(new Opc.Ua.LocalizedText[] { node.DisplayName });
            exportedNode.Description = Export(new Opc.Ua.LocalizedText[] { node.Description });
            exportedNode.WriteMask = (uint)node.WriteMask;
            exportedNode.UserWriteMask = (uint)node.UserWriteMask;

            if (!String.IsNullOrEmpty(node.SymbolicName) && node.SymbolicName != node.BrowseName.Name)
            {
                exportedNode.SymbolicName = node.SymbolicName;
            }

            // export references.
            INodeBrowser browser = node.CreateBrowser(context, null, null, true, BrowseDirection.Both, null, null, true);
            List<Reference> exportedReferences = new List<Reference>();            
            IReference reference = browser.Next();

            while (reference != null)
            {
                Reference exportedReference = new Reference();

                exportedReference.ReferenceType = ExportAlias(reference.ReferenceTypeId, context.NamespaceUris);
                exportedReference.IsForward = !reference.IsInverse;
                exportedReference.Value = Export(reference.TargetId, context.NamespaceUris, context.ServerUris);
                exportedReferences.Add(exportedReference);

                reference = browser.Next();
            }

            exportedNode.References = exportedReferences.ToArray();

            // add node to list.
            UANode[] nodes = null;

            int count = 1;

            if (this.Items == null)
            {
                nodes = new UANode[count];
            }
            else
            {
                count += this.Items.Length;
                nodes = new UANode[count];
                Array.Copy(this.Items, nodes, this.Items.Length);
            }

            nodes[count-1] = exportedNode;

            this.Items = nodes;

            // recusively process children.
            List<BaseInstanceState> children = new List<BaseInstanceState>();
            node.GetChildren(context, children);

            for (int ii = 0; ii < children.Count; ii++)
            {
                Export(context, children[ii]);
            }
        }