Understanding Civil 3D labels and features

By Augusto Goncalves

Civil 3D uses a base class LabelBase to handle labels and the features that it’s being labeled. This is done using the FeatureId property, which is available for all labels. The following code show a generic approach for this.

[CommandMethod("testReadLabelFeature")]public void CmdReadLabelFeature(){  Database db = Application.DocumentManager.MdiActiveDocument.Database;  Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;   PromptEntityOptions peo = new PromptEntityOptions("nSelect a label: ");  peo.SetRejectMessage("nPlease select a Label, try again.");  peo.AddAllowedClass(typeof(LabelBase), true);  PromptEntityResult per = ed.GetEntity(peo);  if (per.Status != PromptStatus.OK) return;   using (Transaction tr = db.TransactionManager.StartTransaction())  {    // open the label    LabelBase genericLabel = tr.GetObject(per.ObjectId,       OpenMode.ForRead) as LabelBase;     // open the entity that this label points to    Autodesk.AutoCAD.DatabaseServices.Entity featureEnt = tr.GetObject(      genericLabel.FeatureId, OpenMode.ForRead)       as Autodesk.AutoCAD.DatabaseServices.Entity;     if (featureEnt != null)    {      // now we know this label points to an entity...       // is it the one we need?      if (featureEnt is Pipe)      {        // is a Pipe, can do something related to PipeLabel        PipeLabel pipeLabel = genericLabel as PipeLabel;        Pipe pipe = featureEnt as Pipe;      }    }    else    {      // make a test to ensure is valid      ed.WriteMessage("nThis label is not linked to an entity. Sorry");    }    tr.Commit();  }}