protected override Autodesk.AutoCAD.EditorInput.SamplerStatus Sampler(Autodesk.AutoCAD.EditorInput.JigPrompts prompts)
        {
            JigPromptPointOptions jigOpts = new JigPromptPointOptions();
            jigOpts.UserInputControls = UserInputControls.GovernedByOrthoMode |  UserInputControls.NullResponseAccepted;
            jigOpts.UseBasePoint = true;
            jigOpts.BasePoint = (Point3d)this.startPoint;
            jigOpts.Message = "\n 选择下一点或者Enter结束";
            PromptPointResult res = prompts.AcquirePoint(jigOpts);
            Point3d positionTemp = res.Value;
            this.endPoint = positionTemp;

            if (res.Status == PromptStatus.Cancel || res.Status == PromptStatus.None)
                return SamplerStatus.Cancel;
            else
                return SamplerStatus.OK;
        }