public bool IsValid() { var oErrors = new List <string>(); if (ToDate <= FromDate) { oErrors.Add("Period final date is less than period start date in " + FromDate.ToString("dd-MM-yyyy", CultureInfo.InvariantCulture) + " and " + ToDate.ToString("dd-MM-yyyy", CultureInfo.InvariantCulture) + "." ); } // if if (string.IsNullOrWhiteSpace(Period)) { Period = ToDate.ToString("MM yy", CultureInfo.InvariantCulture); } if (DueDate < ToDate) { DueDate = ToDate.AddMonths(1).AddDays(7); } if ((BoxData == null) || (BoxData.Count < 1)) { oErrors.Add("No box data specified."); } Errors = oErrors.ToArray(); return(Errors.Length == 0); } // IsValid