private void AddCommand(object model) { ErrorMessage = ""; var customer = model as Customer; if (string.IsNullOrWhiteSpace(customer.CustomerName) || string.IsNullOrWhiteSpace(customer.HouseNumber) || customer.TotalCost < 1) { ErrorMessage = "*Please check the entry. Some field's Values are missing."; return; } customer.CreatedDate = DateTime.Now; customer.SiteId = SiteId; if (_customers.Any(x => x.HouseNumber == customer.HouseNumber)) { if (!OnMessageBoxEvent("House Number you have entered is already booked. Do you still want to continue to add this customer?")) { return; } } _repositoryManager.AddCustomer(customer); Customers = new ObservableCollection <Customer>(_repositoryManager.GetCustomerBySiteId(SiteId)); CustomerToAdd = new Customer(); }