Through the Interface

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.Geometry;

using Autodesk.AutoCAD.Runtime;

 

namespace StrikeText

{

  public class Commands

  {

    [CommandMethod("STXT")]

    public static void StrikeTextArea()

    {

      var doc =

        Application.DocumentManager.MdiActiveDocument;

      var db = doc.Database;

      var ed = doc.Editor;

 

      // Ask for a point. Could also ask for an enclosed text entity

      // and use the picked point or the text's insertion point

 

      var ppo = new PromptPointOptions("\nSelect point");

      var ppr = ed.GetPoint(ppo);

      if (ppr.Status != PromptStatus.OK)

        return;

 

      using (var tr = db.TransactionManager.StartTransaction())

      {

        // Use Editor.TraceBoundary() to check for a suitable

        // boundary. This may throw up a dialog, if selecting a

        // space inside a table, for instance (before you explode

        // it manually). Not ideal - it basically uses the same

        // code path as BHATCH or BOUNDARY, which includes a dialog

 

        var oc = ed.TraceBoundary(ppr.Value, false);

 

        // Only deal with the case where we get a single entity

        // returned

 

        if (oc.Count == 1)

        {

          var ent = oc[0] as Entity;

          if (ent != null)

          {

            // Get the extents of the entity and determine points

            // at the top left and bottom right corners. This is

            // super-simplistic: will only work if we're dealing

            // with a WCS-aligned area. More work needed if dealing

            // with areas with other alignments

 

            var ext = ent.GeometricExtents;

            var pt1 = new Point3d(ext.MinPoint.X, ext.MaxPoint.Y, 0);

            var pt2 = new Point3d(ext.MaxPoint.X, ext.MinPoint.Y, 0);

 

            // Create a line between these points

 

            var ln = new Line(pt1, pt2);

 

            // Add it to the current space

 

            var btr =

              (BlockTableRecord)tr.GetObject(

                db.CurrentSpaceId, OpenMode.ForWrite

              );

            btr.AppendEntity(ln);

            tr.AddNewlyCreatedDBObject(ln, true);

          }

        }

 

        // Commit even if we didn't add anything

 

        tr.Commit();

      }

    }

  }

}