Question

    static BackgroundWorker worker; 
    static void Main(string[] args) 
    { 
      worker = new BackgroundWorker();
      worker.DoWork += worker_DoWork; 
      worker.RunWorkerAsync();
      Console.ReadLine(); 
    } 
    static void worker_DoWork(object sender,DoWorkEventArgs e) 
    { 
      string strClientId = "2211"; Authenticate(ref strClientId); 
    }
    static void Authenticate(ref string strClientId) 
    {
       Timer timer = new Timer(500); 
       //Error in this line 
       //Cannot use ref or out parameter 'strClientId' inside an anonymous method,lambda expression or query expression
       timer.Elapsed += (sender, e) => Authenticates_Timer(sender, e,ref strClientId); 
       //timer.Elapsed += Authenticates_Timer();
       timer.Start(); 
    } 
    static void Authenticates_Timer(object sender, ElapsedEventArgs e, ref string strClientId)
    { 
      //want to use variable here 
      strClientId = "";
    }

如果有办法我可以在传递时使用ref变量参数to event不能使用ref或out参数＆＃39; strClientId＆＃39; 在匿名方法，lambda表达式或查询中表达。我知道这是重复的问题，但我无法做到弄清楚如何解决这个问题已经提到了不同的帖子和在codeproject中也发布了问题，但没有人回应任何问题感谢帮助

Answer 1

我建议将strClientId分享为静态变量：

static BackgroundWorker worker; 
static string strClientId;
static void Main(string[] args) 
{ 
  worker = new BackgroundWorker();
  worker.DoWork += worker_DoWork; 
  worker.RunWorkerAsync();
  Console.ReadLine(); 
} 
static void worker_DoWork(object sender,DoWorkEventArgs e) 
{ 
  strClientId = "2211";
  Authenticate(); 
}
static void Authenticate() 
{
   Timer timer = new Timer(500); 
   timer.Elapsed += (sender, e) => Authenticates_Timer(sender, e); 
   timer.Start(); 
} 
static void Authenticates_Timer(object sender, ElapsedEventArgs e)
{ 
  strClientId = "";
}

它会对你有用吗？

更新：好的，让我们试试这个：

static void worker_DoWork(object sender,DoWorkEventArgs e) 
{ 
  string strClientId = "";
  var setClientId = new Action<string>(v => { strClientId = v; });
  setClientId("2211");
  Authenticate(setClientId); 
}

static void Authenticate(Action<string> setClientId) 
{
  Timer timer = new Timer(500); 
  timer.Elapsed += (sender, e) => Authenticates_Timer(sender, e, setClientId); 
  timer.Start();    
}

static void Authenticates_Timer(object sender, ElapsedEventArgs e, Action<string> setClientId)
{ 
  setClientId("");
}

Answer 2

就这么简单：

static void Authenticate(ref string strClientId) 
{
       Timer timer = new Timer(500); 
       var strClientIdVar = strClientId;
       timer.Elapsed += (sender, e) => Authenticates_Timer(sender, e,ref strClientIdVar);
       timer.Start(); 
}

不能使用使用ref或out参数进行匿名方法

2 个答案: