c# - Why doesn't the status of a task change to canceled after cancel is called by CancellationTokenSource -


i made task count number, task receive cancel request after 5 seconds, after task cancelled checked status of task. status of task still running. why? sample code below:

  var cts = new cancellationtokensource();         cts.cancelafter(5000);//request cancel after 5 seconds         var newtask = task.factory.startnew(state =>         {             try             {                 int = 1;                 var token = (system.threading.cancellationtoken)state;                 while (true)                 {                     console.writeline(i);                     i++;                     thread.sleep(1000);                     token.throwifcancellationrequested();                 }              }             catch             {              }                         {             }           }, cts.token, cts.token);           try         {             newtask.wait(10000, cts.token);          }         catch         {             console.writeline("catch:"+ newtask.status);//the status running         }         console.readline();

there 2 problems code:

  1. token.throwifcancellationrequested() name says, throws exception. since use try/catch block catch might return task. task state after "cancellation" won't faulted because framework doesn't see exception.
  2. you using wait same cancellation token. means 5 seconds done wait cancelled , catch block executed. @ time task may or may not cancelled.

what should getting rid of try/catch/finally in task's body , remove token call wait: newtask.wait(10000).

full code:

var cts = new cancellationtokensource(); cts.cancelafter(5000);//request cancel after 5 seconds var newtask = task.factory.startnew(state => {     int = 1;     var token = (system.threading.cancellationtoken)state;     while (true)     {         console.writeline(i);         i++;         thread.sleep(1000);         token.throwifcancellationrequested();     } }, cts.token, cts.token);  try {     newtask.wait(10000); } catch {     console.writeline("catch:"+ newtask.status); }

linqpad output:

1
2
3
4
5
catch:canceled


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