Item Types

Item Types provide a simplified way for users and applications to create, manage, and use EC data within DgnFiles. More...

Classes
struct	ItemTypeLibraryComponent< T_Impl >
	Base class for a component of an ItemTypeLibrary, i.e., a CustomProperty or CustomPropertyContainer. More...
struct	CustomProperty
	Defines a property within a CustomPropertyContainer. More...
struct	CustomPropertyContainer
	Base class for an object which represents a named collection of CustomProperties within an ItemTypeLibrary. More...
struct	CustomPropertyType
	Defines a collection of properties which can serve as the "type" of a CustomProperty. More...
struct	ItemType
	Defines a named collection of CustomProperties which can be attached to elements, models, and other "item hosts" within a DgnFile. More...
struct	ItemTypeLibrary
	Defines a named collection of ItemTypes and CustomPropertyTypes. More...
struct	ItemTypeLibraries
	Defines a collection of all of the ItemTypeLibrary objects stored within a DgnFile. More...
struct	CustomItemHost
	Represents an object to which a ItemType can be attached to produce an "Item". More...

Detailed Description

Item Types provide a simplified way for users and applications to create, manage, and use EC data within DgnFiles.

An Item Type is an ECClass which supports a subset of the features available to ECClasses. In comparison to full-fledged ECClasses, Item Types:

• Do not support inheritance
• Provide a default value for every primitive property
• Do not support most custom attributes
• Support only a portion of available property types CustomProperty::Type
• Can be used by ItemType-based tools, such as MicroStation's Attach Item tool

Item Types are stored an Item Type Library, which is a similarly restricted ECSchema. In comparison to full-fledged ECSchemas, Item Type Libraries:

• Can reference only standard schemas (chiefly for custom attributes)
• Do not support most custom attributes
• Cannot define custom attribute classes
• Can be freely modified, deleted, updated, and renamed by the user

An Item Type Library is a style-like resource, typically managed using dgnlibs. A management dialog is provided by MicroStation for the end user. Like other styles:

• An ItemTypeLibrary is identified by its name (usually provided by the user)
• A DgnFile which uses an ItemTypeLibrary stores a copy of that library locally
• A local Item Type Library can be replaced with an updated version from a dgnlib
• When copying elements between files, if the element references an ItemTypeLibrary, it will be remapped to use an existing ItemTypeLibrary by the same name in the destination file; or else the ItemTypeLibrary will be copied into the destination file.

Item Types are metadata. They become useful when they are "attached" to a host to produce an Item. An Item is an ECInstance of an Item Type ECClass. Items can be created from Item Types in two ways:

• Using the generic DgnEC APIs defined by DgnECManager and DgnECInstanceEnabler
• Using the ItemType-specific CustomItemHost API Items can be attached to elements, models, indexed views, DgnFiles, and reference attachments. Items attached to elements and models are stored as ECXAttributes in a backward-compatible fashion.

See also

ECObjects

EC Data/Metadata Persistence