선택 Use Selection Filters to Define Selection Set Rules

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;

[CommandMethod("FilterSelectionSet")]
public static void FilterSelectionSet()
{
  // Get the current document editor
  Editor acDocEd = Application.DocumentManager.MdiActiveDocument.Editor;

  // Create a TypedValue array to define the filter criteria
  TypedValue[] acTypValAr = new TypedValue[1];
  acTypValAr.SetValue(new TypedValue((int)DxfCode.Start, "CIRCLE"), 0);

  // Assign the filter criteria to a SelectionFilter object
  SelectionFilter acSelFtr = new SelectionFilter(acTypValAr);

  // Request for objects to be selected in the drawing area
  PromptSelectionResult acSSPrompt;
  acSSPrompt = acDocEd.GetSelection(acSelFtr);

  // If the prompt status is OK, objects were selected
  if (acSSPrompt.Status == PromptStatus.OK)
  {
      SelectionSet acSSet = acSSPrompt.Value;

      Application.ShowAlertDialog("Number of objects selected: " +
                                  acSSet.Count.ToString());
  }
  else
  {
      Application.ShowAlertDialog("Number of objects selected: 0");
  }
}


출처 http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%20.NET%20Developer's%20Guide/index.html