在串口通信中，如果初始化一个不存在的串口
hComm=CreateFile(ComNo,
            GENERIC_READ | GENERIC_WRITE,
           0,
           NULL,
           OPEN_EXISTING,
           0,
           NULL
           );

    if (hComm==INVALID_HANDLE_VALUE)  //
        {
        //MessageBox(0,"error","com error",MB_OK);
        ShowMessage("通信口打开错误"+String(ComNo));
        //return;
        }
程序中为什么有ShowMessage,就报错
“Access violation at address  00000000 .Read of address 00000000”
去掉ShowMessage("通信口打开错误"+String(ComNo));就不回报错，请问是
什么原因？
谢谢！！！