BealeEngineering/BealeEngineering/BealeEngineering.Core/Model/Sale/Invoice.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BealeEngineering.Core.Model.Sale
{
    public class Invoice : InvoiceHeader
    {
        public List<InvoiceLine> InvoiceLineList { get; set; } = new List<InvoiceLine>();

        public bool InvoiceLineListIsSet 
        { 
            get
            {
                if (InvoiceLineList == null || !InvoiceLineList.Any()) { return false; }
                else { return true; }
            } 
        }

        public class InvoiceLine
        {
            [Required(), Range(0, 255)]
            public int LineNumber { get; set; }

            [Required(), StringLength(50)]
            public string InventoryItemCode { get; set; }

            [StringLength(500)]
            public string Description { get; set; }

            [Required(), Range(0, 255)]
            public decimal Quantity { get; set; }

            [Required()]
            public decimal UnitAmount { get; set; }

            [Range(1, 100)]
            public int? Discount { get; set; }

            [Required(), StringLength(10)]
            public string AccountCode { get; set; }

            [Required(), StringLength(50)]
            public string TaxType { get; set; }

            [Required()]
            public decimal TaxAmount { get; set; }

            /// <summary>
            /// Line amount is Tax Exclusive
            /// </summary>
            public decimal LineAmount
            {
                get
                {
                    int discount;
                    if (Discount == null || Discount == 0) { discount = 100; }
                    else { discount = (int)Discount; }
                    return decimal.Round(((Quantity * UnitAmount) * (discount / 100m)),2, MidpointRounding.AwayFromZero);
                }
            }
        }

        public override IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
        {
            base.Validate(validationContext);

            // additional validation
            if (!InvoiceLineListIsSet)
            {
                var result = new ValidationResult("Invoice must have at least one line.");
                ValidationResults.Add(result);
            }
            else
            {
                decimal lineTotal = 0;
                decimal lineTaxTotal = 0;
                foreach (var line in InvoiceLineList)
                {
                    // checks on each line
                    if (line.Quantity <= 0)
                    {
                        var result = new ValidationResult("Quantity must be greater than zero.");
                        ValidationResults.Add(result);
                    }

                    lineTotal = lineTotal + line.LineAmount;
                    lineTaxTotal = lineTaxTotal + line.TaxAmount;
                }
                if (lineTotal + lineTaxTotal != InvoiceTotal)
                {
                    var result = new ValidationResult("Line total is not equal to Invoice Total.");
                    ValidationResults.Add(result);
                }
                if (lineTaxTotal != TaxTotal)
                {
                    var result = new ValidationResult("Line tax total is not equal to Invoice Tax Total.");
                    ValidationResults.Add(result);
                }
            }
            return ValidationResults;
        }
    }
}