public class Customer : IEditableObject 
{
   
    struct CustomerData 
    {
        internal string id ;
        internal string firstName ;
        internal string lastName ;
    }
    
    private CustomersList parent;
    private CustomerData custData; 
    private CustomerData backupData; 
    private bool inTxn = false;

    // Implements IEditableObject
    void IEditableObject.BeginEdit() 
    {
        Console.WriteLine("Start BeginEdit");
        if (!inTxn) 
        {
            this.backupData = custData;
            inTxn = true;
            Console.WriteLine("BeginEdit - " + this.backupData.lastName);
        }
        Console.WriteLine("End BeginEdit");
    }

    void IEditableObject.CancelEdit() 
    {
        Console.WriteLine("Start CancelEdit");
        if (inTxn) 
        {
            this.custData = backupData;
            inTxn = false;
            Console.WriteLine("CancelEdit - " + this.custData.lastName);
        }
        Console.WriteLine("End CancelEdit");
    }

    void IEditableObject.EndEdit() 
    {
        Console.WriteLine("Start EndEdit" + this.custData.id + this.custData.lastName);
        if (inTxn) 
        {
            backupData = new CustomerData();
            inTxn = false;
            Console.WriteLine("Done EndEdit - " + this.custData.id + this.custData.lastName);
        }
        Console.WriteLine("End EndEdit");
    }

    public Customer(string ID) : base() 
    {
        this.custData = new CustomerData();
        this.custData.id = ID;
        this.custData.firstName = "";
        this.custData.lastName = "";
    }

    public string ID 
    {
        get 
        {
            return this.custData.id;
        }
    }
    
    public string FirstName 
    {
        get 
        {
            return this.custData.firstName;
        }
        set 
        {
            this.custData.firstName = value;
            this.OnCustomerChanged();
        }
    }
         
    public string LastName 
    {
        get 
        {
            return this.custData.lastName;
        }
        set 
        {
            this.custData.lastName = value;
            this.OnCustomerChanged();
        }
    }
   
    internal CustomersList Parent 
    {
        get 
        {
            return parent;
        }
        set 
        {
            parent = value ;
        }
    }

    private void OnCustomerChanged() 
    {
        if (!inTxn && Parent != null) 
        {
            Parent.CustomerChanged(this);
        }
    }
    
    public override string ToString() 
    {
        StringWriter sb = new StringWriter();
        sb.Write(this.FirstName);
        sb.Write(" ");
        sb.Write(this.LastName);
        return sb.ToString();
    }   
}