Sequence .Net任務

Question

我有幾個Task的對象，如Task<int>,Task<string>,Task<double>，我想依次運行。也就是說，每個任務完成後，下一個任務自動啓動。每個任務取決於先前任務的輸出。

我該怎麼做？ myTask.ContinueWith（...）重載都假定委託參數。但一個任務不是一個代表。

Answer 1

你可以做這樣的：

var t1 = new Task(() => Console.WriteLine("Completed t1")); 
var t2 = new Task(() => Console.WriteLine("Completed t2")); 
var t3 = new Task(() => Console.WriteLine("Completed t3")); 

t1.ContinueWith(t => t2.RunSynchronously()) 
    .ContinueWith(t => t3.RunSynchronously()); 

t1.Start(); 

---

上面的示例僅適用，如果你不關心的任務的結果。不過，若你（因爲你的編輯狀態），需要每個任務的結果傳遞到下一個任務，那麼你可以這樣做：

var t1 = new Task(() => Console.WriteLine("Completed t1")); 
var t2 = new Task(() => Console.WriteLine("Completed t2")); 
var t3 = new Task(() => Console.WriteLine("Completed t3")); 

t1.ContinueWith(task1 => 
{ 
    Console.WriteLine(task1.Result); 

    t2.ContinueWith(task2 => 
    { 
     Console.WriteLine("{0} | {1}", task1.Result, task2.Result); 

     t3.ContinueWith(task3 => 
     { 
      Console.WriteLine("{0} | {1} | {2}", 
       task1.Result, task2.Result, task3.Result); 
     }); 

     t3.Start(); 
    }); 

    t2.Start(); 
}); 

t1.Start(); 

/* OUTPUT: 
Completed t1 
Completed t1 | Completed t2 
Completed t1 | Completed t2 | Completed t3 */