How to: Navigate Relationships with the UML API

In Visual Studio Ultimate, a model consists of elements linked together by different kinds of relationships. This topic describes how to navigate the model in program code.

Traversing Relationships

Any relationship

Use GetRelatedElements<T>() to find all the elements connected to a specified element. Either set T to IRelationship to traverse relationships of all kinds, or use a more specific type such as IAssociation to traverse just that type.

IElement anElement;
// Select all elements related to anElement.
Context.CurrentDiagram.SelectShapes (

Use GetRelatedLinks<T>() to find all the relationships connected to an element.

// Process all relationships connected to an element.
foreach (IRelationship relationship in 
  Debug.Assert(relationship.SourceElement == anElement
      || relationship.TargetElement == anElement);


An Association is a relationship between two Properties, each of which belongs to a Classifier.

IClassifier classifier; // class, interface, component, actor, ...
// Get all the associations sourced from this classifier
foreach (IProperty p in classifier.GetOutgoingAssociationEnds())
  // p represents the end further end of an association.
  IType oppositeElement = p.Type; 
    // The type to which this association connects classifier
  IProperty oppositeProperty = p.Opposite;
    // The nearer end of the association.
  Debug.Assert(oppositeProperty.Type == classifier);
  IAssociation association = p.Association;
     && association.MemberEnds.Contains(oppositeProperty));

 Generalization and Realization

Access opposite ends of generalization:

foreach (IClassifier supertype in classifier.Generals) {…}
foreach (IClassifier subtype in classifier.GetSpecifics()) {…}
Access the relationship itself:
foreach (IGeneralization gen in classifier.Generalizations) 
{ Debug.Assert(classifier == gen.Specific); }

/// InterfaceRealization:
IEnumerable<IInterface> GetRealizedInterfaces
    (this IBehavioredClassifier classifier);
IEnumerable<IBehavioredClassifier> GetRealizingClassifiers
    (this IInterface interface);


/// Returns the elements depending on this element
IEnumerable<INamedElement> GetDependencyClients(this INamedElement element); 
/// Returns the elements this element depends on
IEnumerable<INamedElement> INamedElement GetDependencySuppliers(this INamedElement element);

Activity Edge

/// Returns the nodes targeted by edges outgoing from this one
IEnumerable<IActivityNode> GetActivityEdgeTargets(this IActivityNode node);
/// Returns the nodes sourcing edges incoming to this one
IEnumerable<IActivityNode> GetActivityEdgeSources(this IActivityNode node);

Connector (assembly and delegation)

/// Returns the elements connected via assembly 
/// or delegation to this one
IEnumerable<IConnectableElement> GetConnectedElements(this IConnectableElement element);

Messages and Lifelines

IEnumerable<IMessage> GetAllOutgoingMessages(this ILifeline  lifeline); 
// both from lifeline and execution occurrences
IEnumerable<IMessage> GetAllIncomingMessages(this ILifeline  lifeline);
ILifeline GetSourceLifeline(this IMessage message); 
    // may return null for found messages
ILifeline GetTargetLifeline(this IMessage message);  
    // may return null for lost messages

Package Import

IEnumerable<IPackage>GetImportedPackages(this INamespace namespace);
IEnumerable<INamespace> GetImportingNamespaces(this IPackage package);

Use case extend and include

IEnumerable<IUseCase>GetExtendedCases(this IUseCase usecase);
IEnumerable<IUseCase>GetExtendingCases(this IUseCase usecase);
IEnumerable<IUseCase>GetIncludedCases(this IUseCase usecase);
IEnumerable<IUseCase>GetIncludingCases(this IUseCase usecase);

 Enumerating Relationships

All properties of the UML model that return multiple values conform to the IEnumerable<> interface. This means that you can use Linq Query Expressions and the extension methods defined in the System.Linq namespace.

For example:

from shape in     Context.CurrentDiagram.GetSelectedShapes<IClassifier>()
where shape.Color == System.Drawing.Color.Red
select shape.Element

See Also


Extending UML Models and Diagrams

How to: Navigate the UML Model