Prototype of what the TransactionViewModel should look like

TransactionViewModel.cs

using Quagga.DbDomain

namespace Quagga.POS
{
  class TransactionViewModel: INotifyPropertyChanged
  {
    private IDbItemCommands _dbItems;
    private IDbTransactionCommands _dbTrans;
    public TransactionViewModel(IDbItemCommands dbItems, IDbTransactionCommands dbTrans)
    {
      _dbItems = dbItems;
      _dbTrans = dbTrans;
      TransactionID = _dbTrans.getTransactionID();
    }
    private List<Item> _transactionList;
    public List<Item> TransactionList
    {
      get
      {
        return _transactionList;
      }
      set
      {
        this._transactionList = value;
        this.NotifyPropertyChanged("TransactionList");
      }
    }
    private string _transactionID;
    public string TransactionID
    {
      get
      {
        return _transactionID;
      }
      protected set
      {
        this._transactionID = value;
        this.NotifyPropertyChanged("TransactionID");
      }
    }
    public AddItemtoTransaction(string UPC)
    {
      Item itemToAdd = _dbItems.getItemByUPC(UPC);
      if (itemToAdd == null)
      {
        throw new ItemNotFoundException("Item " + UPC + "not found in database");
      }
      TransactionList.add(itemToAdd);
    }
    public RingOutTransaction()
    {
      if (TransactionList.count < 1)
      {
        throw new ArgumentException("Must have at least 1 item for a transaction");
      }
      _dbTrans.processTransaction(TransactionID, TransactionList);
      TransactionList.Clear();
      TransactionID = _dbTrans.getTransactionID();
    }
  }
}