windows phone - C# IsolatedStorage problems -

i developing game windows phone using c# xna. unfortunately, xna's storage not supported on windows phone have use c# isolatedstorage, not familiar with. trying make player high score, if players score higher last high score program writes score file stored on device , every time player opens game, high score loaded file , shown them. game seems work fine, tells player have beaten last high score when exit game , run again, high score displayed zero. bug has been killing me. have tried last resort on here.

here class deals storage:

using system; using system.collections.generic; using system.linq; using system.text; using system.io.isolatedstorage; using system.io; using microsoft.xna.framework.graphics; using microsoft.xna.framework;  namespace square_eyes {     class rrsavescore     {         public string highscoreconverted;         public int highscore;          public rrsavescore()          {             highscoreconverted = highscore.tostring();         }          public void writescore(rrscore score, gametime gametime)         {              isolatedstoragefile filestorage = isolatedstoragefile.getuserstoreforapplication();               streamwriter filewriter = new streamwriter             (new isolatedstoragefilestream("newtext.txt", filemode.openorcreate,filestorage));              highscore = score.score;             filewriter.writeline(highscore.tostring());             filewriter.close();         }           public void readscore()          {              isolatedstoragefile filestorage = isolatedstoragefile.getuserstoreforapplication();                 streamreader filereader = null;             try             {                 filereader = new streamreader(new isolatedstoragefilestream                      ("newtext.txt", filemode.open, filestorage));                  highscoreconverted = filereader.readline();                 filereader.close();             }             catch             {                 highscoreconverted = "0";             }         }     } } 

here happens in main game class:

     if (score.score > savescore.highscore)      {            savescore.writescore(score, gametime);            savescore.readscore();      } 

here draw method:

spritebatch.drawstring(font, savescore.highscoreconverted, new vector2(100, 100), color.white); 

i need done, appreciated.