TaskScheduler with async sequential Tasks C#

问题:

I am executing some .py scripts async. One Script takes about 30 seconds to be executed. It could happen that two or even more Scripts are being selected in a timespan of two or three seconds. The Goal is to have a Scheduler which collects all the tasks and executes them one after the other. A FIFO functionality should be included. I 've tried the following Code just to try the functionality of the queuedTaskScheduler, but even that doesn't work.

QueuedTaskScheduler queueScheduler; private TaskScheduler ts_priority1; int pos = 0;         public Form1()     {         InitializeComponent();         queueScheduler = new QueuedTaskScheduler(targetScheduler: TaskScheduler.Default, maxConcurrencyLevel: 1);         ts_priority1 = queueScheduler.ActivateNewQueue(1);     }         private void button3_Click(object sender, EventArgs e)     {         QueueValue(pos, ts_priority1);         pos++;     }      private void button4_Click(object sender, EventArgs e)     {         changeString(pos);         pos++;     }     private void changeString (int position)     {         var bea = "This is Thread " + position + " starting";         MethodInvoker Labelupdate = delegate         {             label2.Text = bea;         };         Invoke(Labelupdate);          Thread.Sleep(3000);         bea = "Thread " + position + " is ending";          MethodInvoker Labelupdate1 = delegate         {             label2.Text = bea;         };         Invoke(Labelupdate1);         Thread.Sleep(1000);     }     private void updateLabel (string Lab)     {         MethodInvoker Labelupdate = delegate         {             label2.Text = Lab;         };         Invoke(Labelupdate);     }     private Task QueueTask(Func<Task> f, TaskScheduler ts)     {         return Task.Factory.StartNew(f, CancellationToken.None, TaskCreationOptions.HideScheduler | TaskCreationOptions.DenyChildAttach, ts);     }      private Task QueueValue(int position, TaskScheduler ts)     {         return QueueTask(async () =>         {             label2.Text = "This is Thread " + position + " starting";             Thread.Sleep(3000);             label2.Text = "Thread " + position + " is ending";             Thread.Sleep(1000);         }, ts);     } 

回答1:

I solved it. There is only need of a Semaphore. It is the same way as in this Thread Here is the Code:

private static SemaphoreSlim semaphore = new SemaphoreSlim(1);  private Task QueueValue(int position, TaskScheduler ts)     {         return QueueTask(async () =>         {             await semaphore.WaitAsync();             try             {                 var at = "This is Thread " + position + " starting";                 updateLabel(at);                 await Task.Delay(3000);                 at = "Thread " + position + " is ending";                 updateLabel(at);                 await Task.Delay(1000);             }             finally             {                  semaphore.Release();             }          }, ts);     } 

Many thanks!

文章来源: TaskScheduler with async sequential Tasks C#