public void AddTransaction(Transaction transaction)
 {
     if(transaction.SellingPrice < 0)
         transaction.SellingPrice = getMRPForInventoryItem(transaction.InventoryItem);
     if (transaction.SaleDate == null)
         transaction.SaleDate = DateTime.Now;
     db.Transactions.InsertOnSubmit(transaction);
     db.SubmitChanges();
 }   
 public void UpdateTransaction(Transaction transaction)
 {
     Transaction transactionToUpdate = db.Transactions.Single(item => item.Id == transaction.Id);
     transactionToUpdate.Quantity = transaction.Quantity;
     transactionToUpdate.SaleDate = transaction.SaleDate;
     transactionToUpdate.InventoryItem = transaction.InventoryItem;
     if (transaction.SellingPrice < 0)
         transactionToUpdate.SellingPrice = getMRPForInventoryItem(transaction.InventoryItem);
     else
         transactionToUpdate.SellingPrice = transaction.SellingPrice;
     db.SubmitChanges();
 }   
 partial void DeleteTransaction(Transaction instance);
		private void detach_Transactions(Transaction entity)
		{
			this.SendPropertyChanging();
			entity.Inventory = null;
		}
 partial void UpdateTransaction(Transaction instance);
 partial void InsertTransaction(Transaction instance);