[求助]关闭文档出错

gsteven

 [CommandMethod("m1")]
        static public void MultiSheetPlot()
        {
            //打开
            Document doc1 = Application.DocumentManager.Open(@"D:\1200图框.dwg", false);
            Application.DocumentManager.MdiActiveDocument = doc1;
        }
        [CommandMethod("m3")]
        static public void MultiSheetPlot3()
        {

Application.DocumentManager.MdiActiveDocument.CloseAndDiscard();
        }

执行m3时cad已经有两个文档，但是出错，为什么呢？

雪山飞狐_lzh

        [CommandMethod("m1", CommandFlags.Session)]
        static public void MultiSheetPlot()
        {
            //打开
            Document doc1 = Application.DocumentManager.Open(@"D:\1200图框.dwg", false);
        }
        [CommandMethod("m3", CommandFlags.Session)]
        static public void MultiSheetPlot3()
        {
            Application.DocumentManager.MdiActiveDocument.CloseAndDiscard();
        }