文件流读写

        ISharedPreferences sp=GetSharedPreferences("login",FileCreationMode.Private);
            string username=sp.GetString("userName","");
   ISharedPreferences sp=GetSharedPreferences("login",FileCreationMode.Private);
            ISharedPreferencesEditor editor = sp.Edit();
            editor.PutString("userName", "uname");
            editor.Commit();