c# - Using Tasks with conditional continuations -

i'm little confused how use tasks conditional continuations.

if have task, , want continue tasks handle success , error, , wait on complete.

void functionthrows() {throw new exception("faulted");}  static void mytest() {      var taskthrows = task.factory.startnew(() => functionthrows());      var onsuccess = taskthrows.continuewith(                           prev => console.writeline("success"),                            taskcontinuationoptions.onlyonrantocompleted);      var onerror = taskthrows.continuewith(                           prev => console.writeline(prev.exception),                           taskcontinuationoptions.onlyonfaulted);      //so far,        //this throws because onsuccess cancelled before started     task.waitall(onsuccess, onerror); } 

is preferred way of doing task success/failure branching? also, how supposed join these tasks, suppose i've created long line of continuations, each having own error handling.

  //for example   var task1 = task.factory.startnew(() => ...)   var task1error = task1.continuewith(  //on faulted   var task2  = task1.continuewith(      //on success   var task2error = task2.continuewith(  //on faulted   var task3 = task2.continuewith(       //on success   //etc 

calling waitall on these invariably throws, because of continuations cancelled due taskcontinuationoptions, , calling wait on cancelled task throws. how join these without getting "a task cancelled" exception"?

i think main problem you're telling 2 tasks "wait" call

task.waitall(onsuccess, onerror); 

the onsuccess , onerror continuations automatically setup , executed after antecedent task completes.

if replace task.waitall(...) taskthrows.start(); believe desired output.

here bit of example put together:

class program {     static int divideby(int divisor)      {        thread.sleep(2000);       return 10 / divisor;      }      static void main(string[] args)     {         const int value = 0;          var exceptiontask = new task<int>(() => divideby(value));          exceptiontask.continuewith(result => console.writeline("faulted ..."), taskcontinuationoptions.onlyonfaulted | taskcontinuationoptions.attachedtoparent);         exceptiontask.continuewith(result => console.writeline("success ..."), taskcontinuationoptions.onlyonrantocompletion | taskcontinuationoptions.attachedtoparent);          exceptiontask.start();          try         {             exceptiontask.wait();         }         catch (aggregateexception ex)         {             console.writeline("exception: {0}", ex.innerexception.message);         }          console.writeline("press <enter> continue ...");         console.readline();     } }