narsil/Tanshu.Accounts.Contracts/Data Contracts Display/BillItemKey.cs

using System;

namespace Tanshu.Accounts.Contracts
{
    public enum BillItemType
    {
        Product,
        Kot
    }
    public class BillItemKey
    {
        private BillItemKey(int productID, int kotID, BillItemType billItemType)
        {
            if (kotID < 0)
                throw new ArgumentException("KotID Cannot be Negative");
            if (productID < 0)
                throw new ArgumentException("ProductID Cannot be Negative");
            BillItemType = billItemType;
            ProductID = productID;
            KotID = kotID;
        }
        public BillItemKey(int kotID)
            : this(0, kotID, BillItemType.Kot)
        { }
        public BillItemKey(int productID, int kotID)
            : this(productID, kotID, BillItemType.Product)
        { }

        private int _productID;
        public int ProductID
        {
            get { return BillItemType == BillItemType.Product ? _productID : 0; }
            private set { _productID = BillItemType == BillItemType.Product ? value : 0; }
        }

        public int KotID { get; private set; }

        public BillItemType BillItemType { get; private set; }
        public override int GetHashCode()
        {
            return BillItemType == BillItemType.Product ?
                ProductID.GetHashCode() ^ KotID.GetHashCode() ^ BillItemType.GetHashCode()
                : KotID.GetHashCode() ^ BillItemType.GetHashCode(); ;
        }
        public override bool Equals(object obj)
        {
            if (obj is BillItemKey)
                return (this == (BillItemKey)obj);
            else
                return false;
        }
        public override string ToString()
        {
            return string.Format("{0} - {1}", ProductID, KotID);
        }

        public static bool operator ==(BillItemKey a, BillItemKey b)
        {
            if (object.ReferenceEquals(null, a))
                return object.ReferenceEquals(null, b);

            if (!(a is BillItemKey))
                return false;
            if (!(b is BillItemKey))
                return false;

            if (a.BillItemType != b.BillItemType)
                return false;

            return a.BillItemType == BillItemType.Product ?
                a.ProductID == b.ProductID && a.KotID == b.KotID && a.BillItemType == b.BillItemType
                : a.KotID == b.KotID && a.BillItemType == b.BillItemType;
        }
        public static bool operator !=(BillItemKey a, BillItemKey b)
        {
            return !(a == b);
        }
    }
}