IRelationshipClass Interface

Provides access to members that return information about the relationship class, create relationships, relationship rules and get related objects. Note: the IRelationshipClass interface has been superseded byIRelationshipClass2. Please consider using the more recent version.

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Description

A RelationshipClass is an association between two object classes; one is the origin class and the other the destination class.  The RelationshipClass can have cardinality taking the form of 1-1, 1-M, M-N (One-to-One, One-to-Many, Many-to-Many).  A RelationshipClass may be simple or composite.  Composite relationship classes are 1-M where the origin class controls the lifetime of the destination class.  Simple relationship classes are peer-to-peer where the related objects can exist independent of each other.

When To Use

Use the RelationshipClass when you want to maintain particular associations between objects in a geodatabase.

Members

	All Properties Methods	Description
	AddRelationshipRule	Adds a relationship rule to this relationship class.
	BackwardPathLabel	The backward path label for the relationship class.
	Cardinality	The cardinality for the relationship class.
	CreateRelationship	Creates a new relationship between the two specified objects.
	DeleteRelationship	Deletes the relationship that associates the two specified objects.
	DeleteRelationshipRule	Deletes a relationship rule from this relationship class.
	DeleteRelationshipsForObject	Deletes all relationships that apply to a specified object.
	DeleteRelationshipsForObjectSet	Deletes all relationships that apply to the specified origin or destination object set.
	DestinationClass	The destination object class.
	DestinationForeignKey	The relationship destination foreign Key.
	DestinationPrimaryKey	The relationship destination primary Key.
	FeatureDataset	The feature dataset, if any, to which this relationship class belongs.
	ForwardPathLabel	The forward path label for the relationship class.
	GetObjectsMatchingObjectSet	Gets rows pairs of objects that are related to the specified origin or destination object set.
	GetObjectsRelatedToObject	Gets the objects that are related to the specified object.
	GetObjectsRelatedToObjectSet	Gets the objects that are related to the specified origin or destination object set.
	GetRelationship	Get the relationship that associates the two specified objects.
	GetRelationshipsForObject	Get all relationships that apply to a specified object.
	GetRelationshipsForObjectSet	Get all relationships that apply to the specified origin or destination object set.
	IsAttributed	Indicates if the relationships in this relationship class have attributes.
	IsComposite	Indicates if the relationship class represents a composite relationship in which the origin object class represents the composite object.
	Notification	The notification direction for the relationship class.
	OriginClass	The origin object class.
	OriginForeignKey	The relationship origin foreign Key.
	OriginPrimaryKey	The relationship origin primary Key.
	RelationshipClassID	The relationship class ID.
	RelationshipRules	The relationship rules that apply to this relationship class.

CoClasses that implement IRelationshipClass

Remarks

Relationships can be between spatial, non-spatial objects, or between spatial and non-spatial objects.  The spatial objects will be stored in feature classes, and the non-spatial in object classes, however, all of the relationships will be maintained in the relationship class.  RelationshipClasses can be created using the IRelationshipClassContainer interface on the FeatureDataset Class.

The IRelationshipClass interface provides information about a relationship class, functionality to create and delete individual relationships, and methods to find related objects. The members of this interface can be split into three logical groups: the properties that correspond to how the relationship class was created, the object-to-object methods that deal with individual relationships, and lastly the relationship rules methods.

The OriginPrimaryKey, OriginForeignKey, DestinationPrimaryKey, and DestinationForeignKey properties can be somewhat confusing—their use is different depending on whether the relationship class is attributed.

The object-to-object methods such as GetObjectsRelatedToObjectSet make a lot of use of the ISet interface, which manipulates a set of generic objects. When adding objects to a set with a cursor, make sure that the cursor is non-recycling.

When using CreateRelationship, remember that this operation will write a value into the foreign key field. Therefore it is possible that you could overwrite, and therefore delete, an existing relationship. Similarly, DeleteRelationship will remove the foreign key value, so that field must allow null values unless you want to ensure that all objects in the class belong to relationships.

The IRelationshipClass::IsAttributed property will only return true if there are extra relationship attributes beyond those required to relate the objects. The IRelationshipClass::GetRelationship method is useful for accessing the relationship attributes.

public void DelRelationships(IRelationshipClass relationshipClass, IFeatureClass featureClass, string whereClause)
{
    // Get the features whose relationships you want to delete
    IQueryFilter queryFilter = new QueryFilterClass();
    queryFilter.WhereClause = whereClause;
    IFeatureCursor featureCursor = featureClass.Search(queryFilter, false);
    IFeature feature = null;
    ISet featureSet = new ESRI.ArcGIS.esriSystem.SetClass();
    while ((feature = featureCursor.NextFeature()) != null) {
      featureSet.Add(feature);
    }
    // Delete the relationships
    featureSet.Reset();
    Console.WriteLine("Count {0}", featureSet.Count);
    relationshipClass.DeleteRelationshipsForObjectSet(featureSet);
}

See Also

ISet Interface

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