编辑多级嵌套对象列表的正确方法

Question

I have 3 objects:

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
    public List<Order> Orders { get; set; }

    public Person()
    {
        Orders= new List<Order>();
    }
}

public class Order
{
    public int Id { get; set; }
    public string Description { get; set; }
    public string Date { get; set; }
    public List<Item> Items { get; set; }

    public Order()
    {
        Items= new List<Item>();
    }
}

public class Item
{
    public int Id { get; set; }
    public string ProductName { get; set; }
    public int Number { get; set; }
}

As You can see every person can have multiple orders and every order can have multiple items.

In my application data that comes from DB looks like so:

private List<Person> _persons;

_persons = new List<Person>
    {
     new Person
      {
       Id = 1,
       Name = "John",
       Surname = "Smith",
       Orders = new List<Order>
        {
         new Order
          {
           Id = 1,
           Description = "First Order",
           Date = "2013-03-07",
           Items =
            new List<Item>
             {
              new Item {Id = 1, Number = 2, ProductName = "Chair"},
              new Item {Id = 2, Number = 1, ProductName = "Bed"}
             }
          },
         new Order
          {
           Id = 2,
           Description = "Second",
           Date = "2013-03-07",
           Items =
            new List<Item>
             {
              new Item {Id = 1, Number = 2, ProductName = "Pen"},
              new Item {Id = 2, Number = 1, ProductName = "Pencil"}
             }
          }
        }
      },
      new Person
      {
       Id = 2,
       Name = "Adam",
       Surname = "West",
       Orders = new List<Order>
        {
         new Order
          {
           Id = 1,
           Description = "Adams order",
           Date = "2013-03-07",
           Items =
            new List<Item>
             {
              new Item {Id = 1, Number = 2, ProductName = "first"},
              new Item {Id = 2, Number = 1, ProductName = "second"}
             }
          },
         new Order
          {
           Id = 2,
           Description = "Adams second",
           Date = "2013-03-07",
           Items =
            new List<Item>
             {
              new Item {Id = 1, Number = 2, ProductName = "Pen"},
              new Item {Id = 2, Number = 1, ProductName = "Pencil"}
             }
          }
        }
      }
    };

I've created custom User control with 2 labels and datagridview like this: below is my code:

using System.Windows.Forms;
using Demo.Model;

namespace Demo.Controls
{
    public partial class OrderView : UserControl
    {
        private Order _order;

        public Order Order
        {
            get { return _order; }
            set
            {
                _order = value;
                UpdateView();
            }
        }

        private void UpdateView()
        {
            if (_order == null) return;
            IdLBL.Text = string.Format("ID: {0}", _order.Id);
            DateLBL.Text = string.Format("Date: {0}", _order.Date);

            ItemsDGV.DataSource = _order.Items;
        }

        public OrderView()
        {
            InitializeComponent();
        }
    }
}

Then in main form I'm adding instances of that control to flowLayoutPanel (for every order for specific person):

private void RefreshView()
{
   flowLayoutPanel1.Controls.Clear();
   foreach (Order order in _persons[_currentPerson].Orders)
   {
      flowLayoutPanel1.Controls.Add(new OrderView {Order = order});
   }
}

With above data my application looks like so:

I need to be able to add/edit every item of every order. Adding seems to be quite easy-I'll create new form, user will input details and then I'll do DB call to add that item.

My questions are:
How can I auto refresh view after add/edit item? Can I somehow bind my control to that list to every time I update it my view updates. I need to be able to add items and orders to person. What would be the easiest way of doing that?

Is this kind of display correct? Can I improve it? If yes then how?

Answer 1

One way to solve this problem would be to use a polling mechanism. This can be plumbed in using the System.Threading.Timer , which uses the System.Threading.ThreadPool.

You would repeatedly query to see if your data has been updated. You'll need to store the modified date with your data, I'd recommend storing it in UTC. Alternatively, you could just use an integer tag that is incremented every time data is updated, then if the tag is out of date, you know you need to update your displayed data.

The dangerous thing about polling refreshes is how much load your server will encounter, but if your concurrent user base is small, this will not be a problem. If you find it causes performance problems, you can adjust your polling interval, incorporate caching techniques, and possibly farm your server(s).

Your new OrderView class will probably look similar to the following:

using System.Windows.Forms;
using Demo.Model;
using System.Threading;

namespace Demo.Controls
{
    public partial class OrderView : UserControl, IDisposable
    {
        private Order _order;
        private Timer poller;

        public Order Order
        {
            get { return _order; }
            set
            {
                _order = value;
                UpdateView();
            }
        }

        private void UpdateView()
        {
            if (_order == null) return;
            IdLBL.Text = string.Format("ID: {0}", _order.Id);
            DateLBL.Text = string.Format("Date: {0}", _order.Date);

            ItemsDGV.DataSource = _order.Items;
        }

        public OrderView()
        {
            InitializeComponent();
            _poller = new Timer(CheckUpdate, null, timeSpan, timeSpan);
        }

        private void CheckUpdate(Object state)
        {
            //Do update check and update Order if it has changed
        }

        public void Dispose()
        {
            if (_poller != null)
            {
                _poller.Dispose();
            }
        }
    }
}