Got this line of code here but its not working.

using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())

        {
            long newSpace = isf.Quota + spaceRequest;
            try
            {
                if(true == isf.IncreaseQuotaTo(newSpace))
                {
                    Debug.WriteLine("success");
                }
                else
                {
                    Debug.WriteLine("unsuccessful");
                }
            }
            catch (Exception e)
            {

                throw;
            }
        }