Do I need to create a new CancellationTokenSource(); after a task cancel?

Question

I have an application like this:

I have an application where a portion of the code runs in a loop with a timer delay. At the start of the application I declare:

public static CancellationTokenSource tokenSource1 = new CancellationTokenSource();
public static bool Timer1Running;

Here’s the looping area:

 while (App.runCardTimer && App.TimerSeconds > 0)
 {
   App.Timer1Running = true;    
   …
   try
   {
      await Task.Delay(1000, App.tokenSource2.Token);
   }
   catch (TaskCanceledException ex) { }
   App.TimerSeconds--;       
   App.Timer1Running = false;    
 }   

My application responds to a click on the screen like this:

wordGrid.GestureRecognizers.Add(       
   new TapGestureRecognizer()      
   {          
      Command = new Command(() =>          
      {          
         App.TimerSeconds = 0;          
         if (App.tokenSource1 != null && App.Timer1Running)          
         {              
            App.tokenSource1.Cancel();          
         }       
      })    
   });

I am confused about the Cancellation Token. Once I issue the statement:

App.tokenSource1.Cancel(); 

Do I need to create a new Cancellation Token like this:

tokenSource1 = new CancellationTokenSource();

Or can I keep reusing?

Answer 1

CancellationTokens as well as tasks are one-time entities and should be thrown away after use.

Basic approach in you case will be:

• create CancellationTokenSource;
• fire task(s) and pass it(them) CancellationToken;
• wait for task(s) completion, cancellation or failure;
• if you need to repeat operation, go to first list item.

Answer 2

If you want to reset the state of the cancellation token, then there is no way to do this. You have to recreate the CancellationTokenSource.