c# - Strange issue with IsolatedStorage in WP7 device -

i have strange problem in windows phone 7 application. need read/write xml file in app , i'm using isolatedstorage collect data. app sends/gets data skydrive why use it.

ok, here function generate exception:

private void createfileintoisolatedstorage(list<record> list)     {         isf = isolatedstoragefile.getuserstoreforapplication();         if(list.count == 0)             list = new list<record>() { new record { date = datetime.today, value = 0 }};          if (isf.fileexists(filename))         {             isf.deletefile(filename);         }          xmlwritersettings xmlwritersettings = new xmlwritersettings();         xmlwritersettings.indent = true;          using (isolatedstoragefile myisolatedstorage = isolatedstoragefile.getuserstoreforapplication())         {             using (isolatedstoragefilestream stream = myisolatedstorage.openfile(filename, filemode.create))             {                 xmlserializer serializer = new xmlserializer(typeof(list<record>));                 using (xmlwriter xmlwriter = xmlwriter.create(stream, xmlwritersettings))                 {                     serializer.serialize(xmlwriter, list);                 }             }         }     } 

problem:

my problem starts when function runs second time. isf.deletefile(filename); throws isolatedstorageexception. , creating stream crashed application.

it's strange cause happens every time run on device, , when use debugger.

so question how can solve or there better ways this?

any appreciated.

possibly it's because @ beginning of method have:

isf = isolatedstoragefile.getuserstoreforapplication(); 

and never dispose of that. then, later, again in using. one's disposed. , next time call createfileintoisolatedstorage, again, again without disposing.

perhaps want:

using (var isf = isolatedstoragefile.getuserstoreforapplication()) {     if(list.count == 0)         list = new list<record>() { new record { date = datetime.today, value = 0 }};      if (isf.fileexists(filename))     {         isf.deletefile(filename);     } } 

although class-scoped isf variable troublesome. if want keep store active, call once , leave open. otherwise, ditch class-scoped variable.

or, might due this, documentation isolatedstoragefile.deletefile?

file deletions subject intermittent failures because files can in use simultaneously operating system features such virus scanners , file indexers. true created files. macintosh users should aware of issue because of frequent indexing. these reasons, important add code code block handles isolatedstorageexception retry deleting file or log failure.

i suggest like:

int retrycount = 0; while (retrycount < maxretrycount && isf.fileexists(filename)) {     try     {         isf.deletefile(filename);     }     catch (isolatedstorageexception)     {         ++retrycount;         // maybe notify user , delay briefly         // or forget retry , log error. let user try again.     } }