Navigate relationships with the UML API


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A model consists of elements linked together by different kinds of relationships. This topic describes how to navigate the model in program code.

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);  

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  

Extend UML models and diagrams
Navigate the UML model