Reading Revit Links hierarchy

By Augusto Goncalves (@augustomaia)

Basically we need to play with GetParentId and GetChilds methods to understand the hierarchy of the linked files. There is also a GetRootId method, but we’re not using here.

From the documentation, we can see that GetParentId results InvalidElementId for root elements, so we do a first run through to find all root elements. Then, for each get again and recursively get the childs again.

It’s not easy to show a hierarchical result, so let’s create a TreeView, as shown below. Note the result is similar to Revit UI. Cool!

public Result Execute(ExternalCommandData commandData,ref string message,ElementSet elements){  // get active document  Document mainDoc = commandData.Application.ActiveUIDocument.Document;   // prepare to show the results...  TreeNode mainNode = new TreeNode();  mainNode.Text = mainDoc.PathName;   // start by the root links (no parent node)  FilteredElementCollector coll = new FilteredElementCollector(mainDoc);  coll.OfClass(typeof(RevitLinkInstance));  foreach (RevitLinkInstance inst in coll)  {    RevitLinkType type = mainDoc.GetElement(inst.GetTypeId()) as RevitLinkType;    if (type.GetParentId() == ElementId.InvalidElementId)    {      TreeNode parentNode = new TreeNode(inst.Name);      mainNode.Nodes.Add(parentNode);       GetChilds(mainDoc, type.GetChildIds(), parentNode);    }  }   // show the results in a form  System.Windows.Forms.Form resultForm = new System.Windows.Forms.Form();  TreeView treeView = new TreeView();  treeView.Size = resultForm.Size;  treeView.Anchor |= AnchorStyles.Bottom | AnchorStyles.Top;  treeView.Nodes.Add(mainNode);  resultForm.Controls.Add(treeView);  resultForm.ShowDialog();   return Result.Succeeded;} private void GetChilds(Document mainDoc, ICollection<ElementId> ids,                        TreeNode parentNode){  foreach (ElementId id in ids)  {    // get the child information    RevitLinkType type = mainDoc.GetElement(id) as RevitLinkType;     TreeNode subNode = new TreeNode(type.Name);    parentNode.Nodes.Add(subNode);     // then go to the next level    GetChilds(mainDoc, type.GetChildIds(), subNode);  }}