OPC Data Client-UA provides static classes with standard Node IDs defined by OPC Foundation: UADataTypeIds, UAMethodIds, UAObjectIds, UAObjectTypeIds, UAReferenceTypeIds, UAVariableIds, and UAVariableTypeIds. You can use properties of these static classes to easily specify “well-known” nodes you need to refer to, for example, the “ObjectsFolder” node which is a common starting node for browsing.

There are following classes with standard Node IDs for OPC-UA:

• UADataTypeIds: A class that declares constants for all Data Types in the Model Design. This class contains definitions for nodes such as BaseDataType, Number, Integer, Boolean, and so on.
• UAMethodIds: A class that declares constants for all MethodIds. in the Model Design.This class contains definitions for method nodes for condition handling, status machine handling, and others.
• UAObjectIds: A class that declares constants for Objects in the Model Design. This class contains definitions for folder nodes such as DataTypesFolder, EventTypesFolder, ObjectsFolder, ObjectTypesFolder, ReferenceTypesFolder, RootFolder, Server, TypesFolder, VariableTypesFolder, ViewsFolder, and others.
• UAObjectTypeIds: A class that declares constants for Object Types in the Model Design. This class contains definitions for nodes such as BaseObjectType, FolderType, and many other object types.
• UAReferenceTypeIds: A class that declares constants for Reference Types in the Model Design. This class contains definitions for nodes such as Aggregates, HasChild, HasComponent, HasProperty, HierarchicalReferences, Organizes, and more.
• UAVariableIds: A class that declares constants for all Variables in the Model Design.
• UAVariableTypeIds: A class that declares constants for all Variable Types in the Model Design.

When you need to pass a standard node to any method, simply use the corresponding property from the static class, such as UAObjectIds.ObjectsFolder.

Reference

OpcLabs.EasyOpcUA Assembly