c# - Accessing and Updating Cached Dictionary -

i have dictionary (concurrent) used map 1 object id another. getting value id based on input key rather expensive, want persist dictionary in server cache.

i have first-blush attempt @ method this, "feels" there better way it:

private string getitem(string cachekey, string itemkey) {     string sfaccountid = null;     concurrentdictionary<string, string> sfaccountmap =             context.cache[cachekey] concurrentdictionary<string, string>;     if(sfaccountmap == null)     {         lock(cachelock)         {             sfaccountmap = context.cache[cachekey] concurrentdictionary<string, string>;             if(sfaccountmap == null)             {                 sfaccountmap = new concurrentdictionary<string, string>();                 sfaccountid = expensivemethodreturnsstring();                 if(!string.isnullorempty(sfaccountid))                 {                     sfaccountmap.tryadd(itemkey, sfaccountid);                 }                 context.cache[cachekey] = sfaccountmap;             }         }     }     else     {         if(sfaccountmap.containskey(itemkey))         {             sfaccountmap.trygetvalue(itemkey, out sfaccountid);         }         else         {             sfaccountmap.tryadd(itemkey, expensivemethodreturnsstring());             lock(cachelock)             {                 context.cache[cachekey] = sfaccountmap;             }         }     }     return sfaccountid; } 

it appears code can simplified, while still doing doing now.

private concurrentdictionary<string, string> getcachedaccountmap(string cachekey) {     var map = context.cache[cachekey] concurrentdictionary<string, string>;     if (map == null)      {         lock (cachelock)          {             map = context.cache[cachekey] concurrentdictionary<string, string>;             if (map == null)                 map = context.cache[cachekey] = new concurrentdictionary<string, string>();         }     }     return map; }  private string getitem(string cachekey, string itemkey) {     return getcachedaccountmap(cachekey)         .getoradd(itemkey, k => expensivemethodreturnsstring()); } 

note: given unlikely have concurrent access cache while account map not yet there, , appears not bad in exceptional case if 1 allocation , call expensive method, getcachedaccountmap method further simplified, not using locks.

private concurrentdictionary<string, string> getcachedaccountmap(string cachekey) {     var map = context.cache[cachekey] concurrentdictionary<string, string>;     if (map == null)          map = context.cache[cachekey] = new concurrentdictionary<string, string>();     return map; }