如何保持寫入文件，直到調用stop方法

Question

我有一種方法可以從設備讀取數據5秒並將其寫入二進制文件。

// Start acquisition 
    try 
    { 
     // create file stream 
     using (FileStream fileStream = new FileStream(filename, FileMode.Create)) 
     { 
      using (BinaryWriter writer = new BinaryWriter(fileStream)) 
      { 
       // start acquisition thread 
     deviceManagerObj.StartAcquisition(deviceManagerObj.deviceConfigurations); 

      // to stop the application after a specified time, get start time 
      DateTime startTime = DateTime.Now; 
      DateTime stopTime = startTime.AddSeconds(numSecondsRunning); 


      // this is the data processing thread; data received from the devices will be written out to a file here 
      while (DateTime.Now < stopTime) 
      { 
       float[] data = deviceManagerObj.ReadData(numValuesAtOnce); 

       // write data to file 
       for (int i = 0; i < data.Length; i++) 
        writer.Write(data[i]); 
      } 
      } 
     } 
    } 
catch (Exception ex) 
{ 
    Console.WriteLine("\t{0}", ex.Message); 
} 
finally 
{ 
    // stop data acquisition 
    deviceManagerObj.StopAcquisition(); 

    Console.WriteLine("Press any key exit..."); 
    Console.ReadKey(true); 
} 

我想打破這兩種方法：啓動和停止。當啓動被調用時，它不斷從設備讀取數據並將其寫入文件。當停止被稱爲它完成一切。我想要做類似下面的事情，但是確保不會阻塞，並且在停止被調用時停止寫入。我怎樣才能正確地做到這一點？我需要單獨的威脅嗎？

public void start() { 
    try 
    { 
     // create file stream 
     using (FileStream fileStream = new FileStream(filename, FileMode.Create)) 
     { 
      using (BinaryWriter writer = new BinaryWriter(fileStream)) 
      { 
       // start acquisition thread\ 
     deviceManagerObj.StartAcquisition(deviceManagerObj.deviceConfigurations); 
       // this is the data processing thread; data received from the devices will be written out to a file here 
       while (true???) // I dont know how to do this 
       { 
       float[] data = deviceManagerObj.ReadData(numValuesAtOnce); 

       // write data to file 
       for (int i = 0; i < data.Length; i++) 
        writer.Write(data[i]); 
     } 
     } 
    } 
} 

public void stop() 
{ 
    // stop data acquisition 
    deviceManagerObj.StopAcquisition(); 

    Console.WriteLine("Press any key exit..."); 
    Console.ReadKey(true); 
} 

Answer 1

使用TPL做這樣的事情：

public class Worker 
{ 
    private CancellationTokenSource m_CancellationTokenSource; 

    public void Start() 
    { 

     m_CancellationTokenSource = new CancellationTokenSource(); 

     var token = m_CancellationTokenSource.Token; 

     Task.Factory.StartNew(() => 
     { 

      //Prepare the things you need to do before the loop, like opening the files and devices 

      while (!token.IsCancellationRequested) 
      { 
       //Do something here like continuously reading and writing 

      } 

     }, token) 
     .ContinueWith(t => 
     { 
      //This will run after stopping, close files and devices here 
     }); 

    } 

    public void Stop() 
    { 
     m_CancellationTokenSource.Cancel(); 
    } 

} 

在這裏，你如何使用：

Worker worker = new Worker(); 

worker.Start(); 

//Do something here 

//After a while 
worker.Stop(); 

請注意，Start方法立即返回，因爲它會運行在線程池中的另一個線程上工作。