ArcObjects Library Reference (GeoDatabase)

MemoryRelationshipClass Class

A relationship class object that is stored in memory.

MemoryRelationshipClass is a non-creatable object. References to non-creatable objects must be obtained through other objects.

Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

Supported Platforms

Windows, Solaris, Linux

Interfaces

Interfaces	Description
IDataset	Provides access to members that supply dataset information.
IRelationshipClass	Provides access to members that return information about the relationship class, create relationships, relationship rules and get related objects.
IRelationshipClass2	Provides access to members that get related object row pairs within a query filter specification.

Remarks

A MemoryRelationshipClass is a type of RelationshipClass in which the origin and destination classes can be from different workspaces and do not need to persist in a geodatabase. For example, the origin class can represent a shapefile while the destination class can represent a table in a personal or File geodatabase. It is stored in memory instead of within a geodatabase like other RelationshipClasses. You can use the MemoryRelationshipClassName object to save and restore a MemoryRelationshipClass.

To create a Relate in ArcMap, a MemoryRelationshipClass must first be created and then assigned to a Layer or StandaloneTable using the IRelationshipClassCollectionEdit interface.

MemoryRelationshipClasses are simple (non-composite), non-attributed RelationshipClasses that do not support relationship rules. When initialized, the notification type is automatically set to esriRelNotificationNone.

MemoryRelationshipClass inherits from a RelationshipClass and although it implements the same interfaces, not all properties and methods are supported. The following is a review of each of these inheritied interfaces and describes which properties and methods behave differently or are not supported with MemoryRelationshipClasses.

IRelationshipClass

The table below describes how the methods and properties from IRelationshipClass are implemented by a MemoryRelationshipClass:

Member	Behavior with a MemoryRelationshipClass
DestinationClass	Returns the OriginForeignClass object specified in the IMemoryRelationshipClassFactory::Open method.
OriginClass	Returns the OriginPrimaryClass object specified in the IMemoryRelationshipClassFactory::Open method.
DestinationForeignKey	Returns an empty string since a MemoryRelationshipClass is not attributed.
DestinationPrimaryKey	Returns an empty string since a MemoryRelationshipClass is not attributed.
FeatureDataSet	Property is not supported. An error will be returned if you try to use this property.
IsAttributed	Returns False since it can't be attributed.
IsComposite	Returns False since it can't be composite.
Notification	Returns esriRelNotificationNone.
RelationshipClassID	Returns -1. This does not need to be set to a meaningful value since a MemoryRelationshipClass is not stored in a geodatabase
RelationshipRules	Property is not supported. An error will be returned if you try to use this property.
AddRelationshipRule	Method is not supported. An error will be returned if you try to use this method.
CreateRelationship	Method is not supported. An error will be returned if you try to use this method.
DeleteRelationship	Method is not supported. An error will be returned if you try to use this method.
DeleteRelationshipRule	Method is not supported. An error will be returned if you try to use this method.
DeleteRelationshipsforObject	Method is not supported. An error will be returned if you try to use this method.
DeleteRelationshipsforObjectSet	Method is not supported. An error will be returned if you try to use this method.
GetRelationship	Method is not supported. An error will be returned if you try to use this method.
GetRelationshipForObject	Method is not supported. An error will be returned if you try to use this method.
GetRelationshipForObjectSet	Method is not supported. An error will be returned if you try to use this method.

Since the origin and destination classes may belong to different workspaces, the methods in IRelationshipClass that involve editing are not available. The properties and methods of IRelationshipClass that are not listed in the table behave the same way with MemoryRelationshipClasses and they do with other RelationshipClasses.

IDataset

The table below describes how the methods and properties from IDataset are implemented by a MemoryRelationshipClass:

Member	Behavior with a MemoryRelationshipClass
BrowseName	You can get, but not set the BrowseName. The BrowseName will be the name given the MemoryRelationshipClass when initialized. If you try to set it an error is returned.
Category	Returns the string "Memory relationship class"
FullName	Returns a MemoryRelationshipClassName object.
Name	Like BrowseName, returns the name given the MemoryRelationshipClass when initialized
PropertySet	Property is not supported. An error will be returned if you try to use this property.
Subsets	Returns a null value.
Type	Returns esriDTRelationshipClass.
Workspace	Returns a null value.
CanCopy	Returns False indicating that it can't be copied.
CanDelete	Returns False indicating that it can't be deleted.
CanRename	Returns true indicating that it can be renamed.
Copy	Method is not supported. An error will be returned if you try to use this method.
Delete	Method is not supported. An error will be returned if you try to use this method.
Rename	Renames the MemoryRelationshipClass to the name given.

IRelationshipClass2

The IRelationshipClass2 interface provides methods that allow a QueryFilter to be applied to the group of rows that match a specified group of rows in the related table. For example, instead of returning all counties in the state of California, a QueryFilter can be used to limit the California counties returned to just those with a population of over 1 million.