的TaskScheduler有限的併發塊本身

Question

我試圖用the following custom task scheduler限制併發Web請求：我使用的是像這樣

：

const int CONCURRENCY_LEVEL = 2; 

static void Main() 
{ 
    TaskFactory factory = new TaskFactory(new LimitedConcurrencyLevelTaskScheduler(CONCURRENCY_LEVEL)); 

    Task.WaitAll(new[] { factory.StartNew(() => SomeAction("first")), factory.StartNew(() => SomeAction("second")) }); 

    Console.WriteLine("All tasks ended");   
    Console.Read(); 
} 

static void SomeAction(string task) 
{ 
    Console.WriteLine(task + " task started"); 
    Console.WriteLine(AnotherTask(task).Result); 
    Console.WriteLine(task + " task ended"); 
} 

static async Task<string> AnotherTask(string task) 
{ 
    return await Task.Run(() => 
    { 
     Console.WriteLine(task + " inner task started"); 
     // imitate web requests 
     Thread.Sleep(200); 
     Console.WriteLine(task + " inner task ended"); 
     return "ok"; 
    }); 
} 

的問題是，內部任務是使用我的LimitedConcurrencyLevelTaskScheduler而不是默認的TaskScheduler。這導致自我閉鎖和輸出是這樣的：

second task started 
first task started 
first inner task started 
second inner task started 
second inner task ended 
first inner task ended 

當我改變CONCURRENCY_LEVEL到3或改變factory到Task.Factory那顯然一切正常，其輸出是這樣的：

first task started 
second task started 
first inner task started 
second inner task started 
second inner task ended 
first inner task ended 
ok 
second task ended 
ok 
first task ended 
All tasks ended 

我不能更改SomeAction中的代碼。我還可以做些什麼？ Microsoft示例中是否存在錯誤？

Answer 1

開始從您的自定義任務調度任務時指定TaskCreationOptions.HideScheduler：

Task.WaitAll(new[] 
{ 
    factory.StartNew(() => SomeAction("first"), TaskCreationOptions.HideScheduler), 
    factory.StartNew(() => SomeAction("second"), TaskCreationOptions.HideScheduler) 
}); 

從MSDN：

HideScheduler被看作是當前防止環境調度調度程序在創建的任務中。這意味着在創建的任務中執行的操作（例如StartNew或ContinueWith）將看到Default作爲當前調度程序。

Answer 2

嘗試

static async Task<string> AnotherTask(string task) 
{ 
    return await Task.Run(() => 
    { 
     Console.WriteLine(task + " inner task started"); 
     // imitate web requests 
     Thread.Sleep(200); 
     Console.WriteLine(task + " inner task ended"); 
     return "ok"; 
    }).ConfigureAwait(false); //<-------- 
}