public EditExpenseModel(long accountId, Guid externalGuid)
 {
     Expense          = ExpenseRepository.GetAccountExpense(externalGuid);
     Categories       = CategoryHelper.GetCategoryNames(accountId);
     Stores           = StoreHelper.GetStoreNames();
     HasSharedAccount = AccountHelper.HasSharedAccount(accountId);
     IsSharedExpense  = Expense.AccountId != accountId;
 }