.NET 4.5輪詢過程示例請

Question

我想要異步運行Windows服務中的長時間運行的進程 - 並每3秒鐘輪詢一次進程並使用SignalR進行報告。下面的代碼將（理論上）以事件爲基礎的方式來做到這一點，但我不希望隨着每一次改變而開始進展。

有人可以請提供一個簡單的例子，說明如何實施這個專門啓動過程和民意調查/報告進展。請記住，我幾年來一直沒有全職開發！

public async Task<string> StartTask(int delay) 
{ 
    var tokenSource = new CancellationTokenSource(); 
    var progress = new Progress<Tuple<Int32, Int32>>(); 

    progress.ProgressChanged += (s, e) => 
    { 
     r2hProcessesProxy.Invoke("DownloadNotify", string.Format("Major={0} - Minor={1}", e.Item1 , e.Item2 )); 
    }; 

    var task = DownloadTask.DoDownload(delay, tokenSource.Token, new Progress<Tuple<Int32,Int32>>(p => new Tuple<Int32, Int32>(0,0))); 

    await task; 

    return "Task result"; 
} 

Answer 1

您可以使用反應式擴展（Rx）來做到這一點。檢查Throttle()方法：https://msdn.microsoft.com/en-us/library/hh229400(v=vs.103).aspx

using System; 
using System.Linq; 
using System.Reactive.Linq; 
using System.Threading.Tasks; 

public class Test 
{ 
    public async Task<string> StartTask(int delay) 
    { 
     var tokenSource = new CancellationTokenSource(); 
     var progress = new Progress<Tuple<Int32, Int32>>(); 

     var observable = Observable.FromEvent<EventHandler<Tuple<Int32, Int32>>, Tuple<Int32, Int32>>(h => progress.ProgressChanged += h, h => progress.ProgressChanged -= h); 
     var throttled = observable.Throttle(TimeSpan.FromSeconds(3)); 

     using (throttled.Subscribe(e => 
     { 
      r2hProcessesProxy.Invoke("DownloadNotify", string.Format("Major={0} - Minor={1}", e.Item1, e.Item2)); 
     })) 
     { 
      await DownloadTask.DoDownload(delay, tokenSource.Token, new Progress<Tuple<Int32, Int32>>(p => new Tuple<Int32, Int32>(0, 0))); 
     } 

     return "result"; 
    } 
} 

檢查http://go.microsoft.com/fwlink/?LinkId=208528更多信息有關RX