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Question

我在 windows phone 8.1 中使用 System.componentmodel 引用来获取 BackgroundWorker，但每次我放置 BackgroundWorker 时它都会给我

错误 CS0246 找不到类型或命名空间名称“BackgroundWorker”（您是否缺少 using 指令或程序集引用？） HealthBand C:\Users\husam\Desktop\Projects\HealthBand\HealthBand\ConnectionManager .cs 16

我尝试添加引用，但它说它已经添加 当我把

using System.ComponentModel;

它说使用指令是不必要的

这是我的代码

using System;
using System.Diagnostics;
using System.Threading.Tasks;
using Windows.Networking;
using Windows.Networking.Sockets;
using Windows.Storage.Streams;
using System.ComponentModel;

namespace HealthBand
{
/// <summary>
/// Class to control the bluetooth connection to the Arduino.
/// </summary>
public class ConnectionManager
{
    private BackgroundWorker dataReadWorker;
    /// <summary>
    /// Socket used to communicate with Arduino.
    /// </summary>
    private StreamSocket socket;

    /// <summary>
    /// DataWriter used to send commands easily.
    /// </summary>
    private DataWriter dataWriter;

    /// <summary>
    /// DataReader used to receive messages easily.
    /// </summary>
    private DataReader dataReader;

    /// <summary>
    /// Thread used to keep reading data from socket.
    /// </summary>


    /// <summary>
    /// Delegate used by event handler.
    /// </summary>
    /// <param name="message">The message received.</param>
    public delegate void MessageReceivedHandler(string message);

    /// <summary>
    /// Event fired when a new message is received from Arduino.
    /// </summary>
    public event MessageReceivedHandler MessageReceived;

    /// <summary>
    /// Initialize the manager, should be called in OnNavigatedTo of main page.
    /// </summary>
    public void Initialize()
    {
        socket = new StreamSocket();
        dataReadWorker = new BackgroundWorker();
        dataReadWorker.WorkerSupportsCancellation = true;
        dataReadWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);
    }

    /// <summary>
    /// Finalize the connection manager, should be called in OnNavigatedFrom of main page.
    /// </summary>
    public void Terminate()
    {
        if (socket != null)
        {
            socket.Dispose();
        }
        if (dataReadWorker != null)
        {
            dataReadWorker.CancelAsync();
        }
    }

    /// <summary>
    /// Connect to the given host device.
    /// </summary>
    /// <param name="deviceHostName">The host device name.</param>
    public async void Connect(HostName deviceHostName)
    {
        if (socket != null)
        {
            await socket.ConnectAsync(deviceHostName, "1");
            dataReader = new DataReader(socket.InputStream);
            dataReadWorker.RunWorkerAsync();
            dataWriter = new DataWriter(socket.OutputStream);
        }
    }

    /// <summary>
    /// Receive messages from the Arduino through bluetooth.
    /// </summary>
    private async void ReceiveMessages(object sender, DoWorkEventArgs e)
    {
        try
        {
            while (true)
            {
                // Read first byte (length of the subsequent message, 255 or less). 
                uint sizeFieldCount = await dataReader.LoadAsync(1);
                if (sizeFieldCount != 1)
                {
                    // The underlying socket was closed before we were able to read the whole data. 
                    return;
                }

                // Read the message. 
                uint messageLength = dataReader.ReadByte();
                uint actualMessageLength = await dataReader.LoadAsync(messageLength);
                if (messageLength != actualMessageLength)
                {
                    // The underlying socket was closed before we were able to read the whole data. 
                    return;
                }
                // Read the message and process it.
                string message = dataReader.ReadString(actualMessageLength);
                MessageReceived(message);
            }
        }
        catch (Exception ex)
        {
            Debug.WriteLine(ex.Message);
        }

    }

    /// <summary>
    /// Send command to the Arduino through bluetooth.
    /// </summary>
    /// <param name="command">The sent command.</param>
    /// <returns>The number of bytes sent</returns>
    public async Task<uint> SendCommand(string command)
    {
        uint sentCommandSize = 0;
        if (dataWriter != null)
        {
            uint commandSize = dataWriter.MeasureString(command);
            dataWriter.WriteByte((byte)commandSize);
            sentCommandSize = dataWriter.WriteString(command);
            await dataWriter.StoreAsync();
        }
        return sentCommandSize;
    }
}
}

请问我该如何解决这个错误

Answer 1

BackgroundWorker 在 WP8.1 中不受支持。不要使用它，而是使用 Task.Run 方法将您的工作重定向到 ThreadPool。正如文章Asynchronous Programming with Async and Await 所说：

在几乎所有情况下，基于异步的异步编程方法都优于现有方法。特别是，对于 IO 绑定操作，这种方法比 BackgroundWorker 更好，因为代码更简单，您不必防范竞争条件。与 Task.Run 结合使用时，对于 CPU 密集型操作，异步编程比 BackgroundWorker 更好，因为异步编程将运行代码的协调细节与 Task.Run 转移到线程池的工作分开。

如需更多修复、代码示例和比较，请访问Stephen Cleary's blog。