我是否使用 ref 正确传递我的参数？
SMSCOMMS SMSEngine = new SMSCOMMS("COM6");
该代码似乎没有将我的 COM6 参数作为有效的ref string。我该如何解决这个问题？
public class SMSCOMMS
{
public SMSCOMMS(ref string COMMPORT)
{
SMSPort = new SerialPort();
SMSPort.PortName = COMMPORT;
SMSPort.BaudRate = 9600;
SMSPort.Parity = Parity.None;
SMSPort.DataBits = 8;
SMSPort.StopBits = StopBits.One;
SMSPort.Handshake = Handshake.RequestToSend;
SMSPort.DtrEnable = true;
SMSPort.RtsEnable = true;
SMSPort.NewLine = System.Environment.NewLine;
ReadThread = new Thread(
new System.Threading.ThreadStart(ReadPort));
}
SMSCOMMS SMSEngine = new SMSCOMMS("COM6");
The code doesn't seem to take my argument of COM6 as a valid ref string.How can I solve this?
public class SMSCOMMS
{
public SMSCOMMS(ref string COMMPORT)
{
SMSPort = new SerialPort();
SMSPort.PortName = COMMPORT;
SMSPort.BaudRate = 9600;
SMSPort.Parity = Parity.None;
SMSPort.DataBits = 8;
SMSPort.StopBits = StopBits.One;
SMSPort.Handshake = Handshake.RequestToSend;
SMSPort.DtrEnable = true;
SMSPort.RtsEnable = true;
SMSPort.NewLine = System.Environment.NewLine;
ReadThread = new Thread(
new System.Threading.ThreadStart(ReadPort));
}
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评论（3）
您不能使用
ref传递临时值，因为被调用的方法必须能够分配给调用者的变量。你为什么要使用它？您永远不会分配给COMMPORT。为什么不只是：
You can't pass a temporary with
ref, because the called method must be able to assign to the caller's variable. Why are you using it to begin with? You never assign toCOMMPORT.Why not just:
除非您打算修改调用者传递的实际变量，否则无需传递
ref参数。由于您无法修改字符串文字（根据定义，它是常量），因此它对于按引用传递无效。There's no need to pass a
refparam unless you're intending to modify the actual variable the caller's passed. Since you can't modify a string literal (it's constant, by definition), it's not valid for passing by reference.仅当传递具有可用引用的内容时，才能使用
ref。这意味着您必须首先声明一个变量，然后通过 ref 传递该变量：You can only use
refwhen you are passing something that has a usable reference. That means you have to declare a variable first, then pass that variable by ref: