C#-方法-用Cad com获取选择集

        [DllImport("User32.dll", CharSet = CharSet.Unicode)]
        public static extern bool SetForegroundWindow(IntPtr hWnd);
        public static AcadSelectionSet SelectEntityOnScreen(this AcadApplication Ca, short[] groupcpde, object[] datacode, string strSsetname = "SELECTION~TEXT~1111")
        {
            AcadDocument zdoc = Ca.ActiveDocument;
            foreach (AcadSelectionSet SetItem in zdoc.SelectionSets)
            {
                if (SetItem.Name == strSsetname)
                {
                    SetItem.Delete();
                    break;
                }
            }
            AcadSelectionSet objSset = zdoc.SelectionSets.Add(strSsetname);
            SetForegroundWindow((IntPtr)Ca.HWND);
            objSset.SelectOnScreen(groupcpde, datacode);
            return objSset;
        }