用keyword实现Editor.GetSelection的退出功能

[CommandMethod("SELKW")]
publicvoid GetSelectionWithKeywords()
{
    Document doc =
        Application.DocumentManager.MdiActiveDocument;
    Editor ed = doc.Editor;
 
    // Create our options object
    PromptSelectionOptions pso = newPromptSelectionOptions();
 
    // Add our keywords
    pso.Keywords.Add("FIrst");
    pso.Keywords.Add("Second");
 
    // Set our prompts to include our keywords
    string kws = pso.Keywords.GetDisplayString(true);
    pso.MessageForAdding =
                "\nAdd objects to selection or " + kws;
    pso.MessageForRemoval =
            "\nRemove objects from selection or " + kws;
 
    pso.KeywordInput +=
           newSelectionTextInputEventHandler(pso_KeywordInput);
 
    PromptSelectionResult psr = null;
    try
    {
        psr = ed.GetSelection(pso);
 
        if (psr.Status == PromptStatus.OK)
        {
            //your logic
        }
    }
    catch (System.Exception ex)
    {
        if (ex is Autodesk.AutoCAD.Runtime.Exception)
        {
            Autodesk.AutoCAD.Runtime.Exception aEs =
                    ex as Autodesk.AutoCAD.Runtime.Exception;
 
            //user has pressed keyword.
 
            if (aEs.ErrorStatus ==
                        Autodesk.AutoCAD.Runtime.ErrorStatus.OK)
            {
                ed.WriteMessage("\nKeyword entered: {0}",
                                                     ex.Message);
            }
            else
            {
                //other exception, please handle
            }
        }
    }
 
}
void pso_KeywordInput(object sender, SelectionTextInputEventArgs e)
{
    //user has pressed keyword, so throw Exception
    throw new Autodesk.AutoCAD.Runtime.Exception(
                Autodesk.AutoCAD.Runtime.ErrorStatus.OK, e.Input);
}