c# - Problems with System.Threading.Timer in PCL Profile 78 - Warnings -

i surprised convenient system.threading.timer class not exist in profile 78 libraries. use class created pcl targets 4.0 framework , wrote simple wrapper around (as suggested in 1 blog post):

public class pcltimer {     private timer timer;     private action<object> action;      public pcltimer (action<object> action, object state, int duetimemilliseconds, int periodmilliseconds)     {         this.action = action;         timer = new timer (pcltimercallback, state, duetimemilliseconds, periodmilliseconds);     }      private void pcltimercallback (object state)     {         action.invoke (state);     }      public bool change (int duetimemilliseconds, int periodmilliseconds)     {         return timer.change (duetimemilliseconds, periodmilliseconds);     } } 

now can reference 4.0 library , use pcltimer in main pcl library. when try build main android project following warnings:

warning cs1684: reference type 'system.threading.timer' claims defined in 'c:\program files (x86)\reference assemblies\microsoft\framework\.netportable\v4.5\profile\profile78\mscorlib.dll', not found (cs1684) (prototype.core)  warning msb3247: found conflicts between different versions of same dependent assembly. (msb3247) (prototype.droid) 

how rid of these warnings properly?

here complete re-implementation of timer class temporarily disappeared in profile 78, using asynchronous tasks:

using system; using system.threading; using system.threading.tasks;  namespace quantum {     public delegate void timercallback(object state);      public sealed class timer : idisposable     {         private static task completedtask = task.fromresult(false);          private timercallback callback;         private task delay;         private bool disposed;         private int period;         private object state;         private cancellationtokensource tokensource;          public timer(timercallback callback, object state, int duetime, int period)         {             callback = callback;             state = state;             period = period;             reset(duetime);         }          public timer(timercallback callback, object state, timespan duetime, timespan period)             : this(callback, state, (int)duetime.totalmilliseconds, (int)period.totalmilliseconds)         {         }          ~timer()         {             dispose(false);         }          public void dispose()         {             dispose(true);             gc.suppressfinalize(this);         }          private void dispose(bool cleanupmanagedobjects)         {             if (cleanupmanagedobjects)                 cancel();             disposed = true;         }          public void change(int duetime, int period)         {             period = period;             reset(duetime);         }          public void change(timespan duetime, timespan period)         {             change((int)duetime.totalmilliseconds, (int)period.totalmilliseconds);         }          private void reset(int due)         {             cancel();             if (due >= 0)             {                 tokensource = new cancellationtokensource();                 action tick = null;                 tick = () =>                 {                     task.run(() => callback(state));                     if (!disposed && period >= 0)                     {                         if (period > 0)                             delay = task.delay(period, tokensource.token);                         else                             delay = completedtask;                         delay.continuewith(t => tick(), tokensource.token);                     }                 };                 if (due > 0)                     delay = task.delay(due, tokensource.token);                 else                     delay = completedtask;                 delay.continuewith(t => tick(), tokensource.token);             }         }          private void cancel()         {             if (tokensource != null)             {                 tokensource.cancel();                 tokensource.dispose();                 tokensource = null;             }         }     } }