c# - Locking across different threads in an ASP.NET WebAPI -


i've got scenario require cache information webapi temporarily when first called. same parameters api can called few times second.

due performance restrictions don't want each call fetching data , putting memory cache i've implemented system semaphores try , allow 1 thread initialize cache , allow rest query cache.

i've stripped down code show example of i'm doing currently.

      private static memorycacher memcacher = new memorycacher();       private static concurrentdictionary<string, semaphore> dictionary = new concurrentdictionary<string, semaphore>();                       private async task<int[]> doathing(string requesthash)       {                         // check existing cached result before hitting dictionary              var cachevalue = memcacher.getvalue(requesthash);              if (cachevalue != null)              {                                          return ((cachedresult)cachevalue).cheeseburgers;              }               semaphore semi;              semi = dictionary.getoradd(requesthash, new semaphore(1, 1, requesthash));                                semi.waitone();               //it's possible previous thread has filled cache. have squiz.              cachevalue = memcacher.getvalue(requesthash);              if (cachevalue != null)              {                                      dictionary.tryremove(requesthash);                         semi.release();                                  return ((cachedresult)cachevalue).cheeseburgers;                                         }               // fetch latest data relevant web api              var response = await httpclient.postasync(url, content);                                    // add result cache              memcacher.add(requesthash, new cachedresult() { cheeseburgers = response.returnarray }, datetime.now.addseconds(30));               // have added cacher don't need semaphore in dictonary anymore:              dictionary.tryremove(requesthash);               //open floodgates              semi.release()                return response.returnarray;       }

unfortunately there many weird issues more 1 thread @ time manages through waitone() call , when released manages break due count restriction on semaphore. (to make sure 1 semaphore working @ time) i've tried using mutexes , monitors, since iis doesn't guarantee api call run on same thread causes fail regularly when mutex attempted released in different thread.

any suggestions on other ways implement welcome well!


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