将一个方法传递给后台工作者DoWork

Question

在下面的代码中，有没有一种方法可以不总是订阅updateWorker_DoWork方法，而是传递像这样的一个方法？

public void GetUpdates(SomeObject blah)
{
    //...
    updateWorker.DoWork += new DoWorkEventHandler(blah);
    //...
}


public void GetUpdates()
{
    //Set up worker
    updateWorker.WorkerReportsProgress = true;
    updateWorker.WorkerSupportsCancellation = true;
    updateWorker.DoWork += new DoWorkEventHandler(updateWorker_DoWork);
    updateWorker.RunWorkerCompleted +=
        new RunWorkerCompletedEventHandler(updateWorker_RunWorkerCompleted);
    updateWorker.ProgressChanged +=
        new ProgressChangedEventHandler(updateWorker_ProgressChanged);

    //Run worker
    _canCancelWorker = true;
    updateWorker.RunWorkerAsync();
    //Initial Progress zero percent event
    _thes.UpdateProgress(0);
}

- James

Answer 1

对于您的RunWorkerAsync()，您可以传递任何参数。您可以将Func()或Action()放入其中，在DoWork()中，只需将对象强制转换回此特定类型并调用它即可。

示例在这里和这里。

private void InitializeBackgroundWorker()
{
    _Worker = new BackgroundWorker();

    // On a call cast the e.Argument to a Func<TResult> and call it...
    // Take the result from it and put it into e.Result
    _Worker.DoWork += (sender, e) => e.Result = ((Func<string>)e.Argument)();

    // Take the e.Result and print it out
    // (cause we will always call a Func<string> the e.Result must always be a string)
    _Worker.RunWorkerCompleted += (sender, e) =>
    {
        Debug.Print((string)e.Result);
    };
}

private void StartTheWorker()
{
    int someValue = 42;

    //Take a method with a parameter and put it into another func with no parameter
    //This is called currying or binding
    StartTheWorker(new Func<string>(() => DoSomething(someValue)));

   while(_Worker.IsBusy)
       Thread.Sleep(1);

   //If your function exactly matches, just put it into the argument.
   StartTheWorker(AnotherTask);
}

private void StartTheWorker(Func<string> func)
{
    _Worker.RunWorkerAsync(func);
}

private string DoSomething(int value)
{
    return value.ToString("x");
}

private string AnotherTask()
{
    return "Hello World";
}

- Oliver

---

谢谢。如果我想将委托传递给StartTheWorker函数，参数类型会是什么？实质上，我想能够调用StartTheWorker（DoSomething），并使DoSomething作为后台工作程序运行。 - James

@James：这只是另一个需要用Func()构建的包装器。我更新了示例以反映这一点。 - Oliver

Answer 2

如果我没有误解您的意思，您需要lambda表达式来构建匿名方法。

updateWorker.DoWork += (sender,e)=>
  {
      //bla
  }

现在您不必总是编写一个方法并将其传递给 new DoWorkEventHandler(myMethod)。

- Cheng Chen

Answer 3

解决了，比我想象的简单多了。只需要为在DoWork上调用的方法创建一个委托即可。可能我原来的问题表述不太好。

    public delegate void DoWorkDelegate(object sender,DoWorkEventArgs e);

     public void GetUpdates()
     {
         StartWorker(new DoWorkDelegate(updateWorker_DoWork));
     }

     public void StartWorker(DoWorkDelegate task)
     {
         //Set up worker
         updateWorker.WorkerReportsProgress = true;
         updateWorker.WorkerSupportsCancellation = true;
         updateWorker.DoWork += new DoWorkEventHandler(task);
         updateWorker.RunWorkerCompleted +=
             new RunWorkerCompletedEventHandler(updateWorker_RunWorkerCompleted);
         updateWorker.ProgressChanged +=
             new ProgressChangedEventHandler(updateWorker_ProgressChanged);

         //Run worker
         _canCancelWorker = true;
         updateWorker.RunWorkerAsync();
         //Initial Progress zero percent event
         _thes.UpdateProgress(0);
     }

      private void updateWorker_DoWork(object sender, DoWorkEventArgs e)
      {
          BackgroundWorker worker = sender as BackgroundWorker;
          e.Result = GetUpdatesTask(worker, e);
      }

- James