ElementWalker Class

Definition

Namespace:

Microsoft.VisualStudio.Modeling

Assembly:

Microsoft.VisualStudio.Modeling.Sdk.dll

Package:

Microsoft.VisualStudio.Modeling.Sdk v17.10.40171

Class to enable various traversals of the model starting from a particular element.

public ref class ElementWalker abstract

public abstract class ElementWalker

type ElementWalker = class

Public MustInherit Class ElementWalker

Inheritance

Object

ElementWalker

Derived

Microsoft.VisualStudio.Modeling.BreadthFirstRolePlayerFirstElementWalker

Microsoft.VisualStudio.Modeling.DepthFirstElementWalker

Constructors

ElementWalker(IElementVisitor, IElementVisitorFilter, Boolean)	Constructor that takes an ElementVisitor.
ElementWalker(IElementVisitor, IElementVisitorFilter)	Constructor that takes an ElementVisitor.

Properties

BypassDemandLoading	Allows the walker to bypass demand loading while traversing
Filter	Get or set the IElementVisitorFilter for use during traversal
IncludeLinks	Returns true if the walker will include element links in calls to the visitor function
InternalElementList	Get the internal list of elements that will be visited
Store	Get the internal list of elements that will be visited
Visitor	Get or set the IElementVisitor for use during traversal

Methods

DoTraverse(ModelElement)	Traverse the model starting at the specified starting element.
MarkForRemovalFromInternalElementList(ModelElement)	Mark an element for removal from the InternalElementList. We mark first and remove later at the end so that the indices remain valid. When marking elements as visited, we store an index in the hashtable which tells us the order that the element was visited in. If the elements were put into the InternalElementList in that order, we can find the element easily using the index. If not a linear search will be used to find the element.
MarkVisited(ModelElement)	Mark an element as having been already visited
RemoveMarkedElements()	Removes the elements that are marked for removal. Call this at the end of the traversal so that the indices in alreadyVisited remain valid.
Reset()	Reset the visitor so that it can start traversing again. This is necessary to clear out the internal list of previously visited elements.
ShouldVisitLinkAgain(ElementLink, ModelElement)	When looking at the related elements of the given currentElement, if we find a link that has been enqueued for visiting, this function will tell you if it needs to be visited again. This is if the link has been visited before the currentElement (one of its roleplayers) was visited. For closure walkers, we guarantee that the link will be visited only after the roleplayers are visited (technically, we guarantee that the InternalElementList will contain the link after the roleplayers). Consider this scenario: We have element A that is a roleplayer for 2 relationships AHasBs and CHasAs. During the closure traversal, A is first approached from B through AHasBs. However, it does not have prop-delete on it, so it is not visited but the AHasBs is visited. Later in the traversal, A is approached from C via CHasAs. This time, A is visited because it has prop-delete. Now we get a case where AHasBs was visited before one of its roleplayers (A) was visited. To fix this, if the walkers find that a link has been visited (or rather, been enqueued for visiting) , it should check if it should be visited again (check if it was already visited before currentElement). If so, it should remove the link from the InternalElementList using the methods MarkForRemovalFromInternalElementList and RemoveMarkedElements, and add it to the queue to be visited again.
Traverse(ICollection<ModelElement>)	Traverse the model starting at the specified starting elements.
Traverse(ModelElement)	Traverse the model starting at the specified starting element.
Visited(ModelElement)	determines if the given element has been visited or not