public async Task <string> GenerateTransactionCode() { var lastGeneratedCode = await _transRepo.GetLastGeneratedCode(); if (string.IsNullOrWhiteSpace(lastGeneratedCode)) { return("YOU0000001"); } var stringDigit = lastGeneratedCode.Substring(3); var nextDigit = (Int64.Parse(stringDigit) + 1).ToString().PadLeft(7, '0'); return("YOU" + nextDigit); }