向后台工作者发送参数？

Question

假设我想向后台工作者发送一个 int 参数，如何实现？

private void worker_DoWork(object sender, DoWorkEventArgs e) {

}

我知道这是worker.RunWorkerAsync();，我不明白如何在worker_DoWork中定义它应该采用int参数。

Answer 1

你这样开始：

int value = 123;
bgw1.RunWorkerAsync(argument: value);  // the int will be boxed

然后

private void worker_DoWork(object sender, DoWorkEventArgs e) 
{
   int value = (int) e.Argument;   // the 'argument' parameter resurfaces here

   ...

   // and to transport a result back to the main thread
   double result = 0.1 * value;
   e.Result = result;
}


// the Completed handler should follow this pattern 
// for Error and (optionally) Cancellation handling
private void worker_Completed(object sender, RunWorkerCompletedEventArgs e) 
{
  // check error, check cancel, then use result
  if (e.Error != null)
  {
     // handle the error
  }
  else if (e.Cancelled)
  {
     // handle cancellation
  }
  else
  {          
      double result = (double) e.Result;
      // use it on the UI thread
  }
  // general cleanup code, runs when there was an error or not.
}

Answer 2

尽管这是一个已经回答的问题，但我会留下另一个选项，IMO 更容易阅读：

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += (obj, e) => WorkerDoWork(value, text);
worker.RunWorkerAsync();

在处理程序方法上：

private void WorkerDoWork(int value, string text) {
    ...
}

Answer 3

您可以像这样传递多个参数。

List<object> arguments = new List<object>();
arguments.Add("first");      //argument 1
arguments.Add(new Object()); //argument 2
// ...
arguments.Add(10);           //argument n

backgroundWorker.RunWorkerAsync(arguments);

private void worker_DoWork(object sender, DoWorkEventArgs e) 
{
  List<object> genericlist = e.Argument as List<object>;
  //extract your multiple arguments from 
  //this list and cast them and use them. 
}

Answer 4

您可以使用 DoWorkEventArgs.Argument 属性。

完整的示例（甚至使用 int 参数）可以在 Microsoft 的网站上找到：

• 如何：在后台运行操作

Answer 5

查看 DoWorkEventArgs.Argument 属性：

...
backgroundWorker1.RunWorkerAsync(yourInt);
...

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    // Do not access the form's BackgroundWorker reference directly.
    // Instead, use the reference provided by the sender parameter.
    BackgroundWorker bw = sender as BackgroundWorker;

    // Extract the argument.
    int arg = (int)e.Argument;

    // Start the time-consuming operation.
    e.Result = TimeConsumingOperation(bw, arg);

    // If the operation was canceled by the user, 
    // set the DoWorkEventArgs.Cancel property to true.
    if (bw.CancellationPending)
    {
        e.Cancel = true;
    }
}

Answer 6

如果您想传递多种类型的参数，您可以尝试一下，首先将它们全部添加到 Object 类型的数组中，然后将该对象传递给 RunWorkerAsync() 这是一个示例：

   some_Method(){
   List<string> excludeList = new List<string>(); // list of strings
   string newPath ="some path";  // normal string
   Object[] args = {newPath,excludeList };
            backgroundAnalyzer.RunWorkerAsync(args);
      }

现在在后台工作程序的 doWork 方法中

backgroundAnalyzer_DoWork(object sender, DoWorkEventArgs e)
      {
        backgroundAnalyzer.ReportProgress(50);
        Object[] arg = e.Argument as Object[];
        string path= (string)arg[0];
        List<string> lst = (List<string>) arg[1];
        .......
        // do something......
        //.....
       }

Answer 7

您需要 RunWorkerAsync(object) 方法和 DoWorkEventArgs.Argument 属性。

worker.RunWorkerAsync(5);

private void worker_DoWork(object sender, DoWorkEventArgs e) {
    int argument = (int)e.Argument; //5
}

Answer 8

您应该始终尝试使用具有具体类型的复合对象（使用复合设计模式）而不是对象类型列表。谁会记得这些物体到底是什么？稍后考虑维护代码......相反，尝试这样的事情：

Public (Class or Structure) MyPerson
                public string FirstName { get; set; }
                public string LastName { get; set; }
                public string Address { get; set; }
                public int ZipCode { get; set; }
End Class

然后：

Dim person as new MyPerson With { .FirstName = “Joe”,
                                  .LastName = "Smith”,
                                  ...
                                 }
backgroundWorker1.RunWorkerAsync(person)

然后：

private void backgroundWorker1_DoWork (object sender, DoWorkEventArgs e)
{
        MyPerson person = e.Argument as MyPerson
        string firstname = person.FirstName;
        string lastname = person.LastName;
        int zipcode = person.ZipCode;                                 
}