mscomm 程序问题

Question

try
            {
                if (!comm.PortOpen)
                {
                    comm.PortOpen = true;
                }
                comm.Output = "AT+CMGF=1"+"\r";
                comm.Output = "AT+CSCA="+"\"8613800510500\""+ "\r";
                //Console.WriteLine(comm.Output.ToString());
                //comm.Output = "AT+CMGW=" +"test"+ "\r";
                comm.Output = "AT+CMGS=" + "\"15061812816\"" + "\r";
                comm.Output = "test" + Keys.ControlKey + Keys.Z; //System.Text.Encoding.ASCII.GetBytes("\x1A");
                //Console.WriteLine(comm.Output.ToString());
                
                comm.PortOpen = false;
            }catch(Exception e){
                Console.WriteLine("error");
            }连接没问题为什么发不出短信去 ?请高手指教