#眉標=LINQ	
#副標=剖析LINQ運作機制（7）
#大標= LINQ To SQL與N-Tier應用程式
#作者=文／圖		黃忠成
#引言=



==<box>===========
程式1
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;
namespace WCFDataService
{
    [ServiceContract]
    public interface IDataService
    {
        [OperationContract]
        Customer[] GetAllData();
    }
    public class DataService : IDataService
    {
        #region IDataService Members

        public Customer[] GetAllData()
        {
            NorthwindDataContext context = new NorthwindDataContext();
            return (from s1 in context.Customers select s1).ToArray();
        }
        #endregion
    }
}
==<end>==============




==<box>===========
程式2
private void Window_Loaded(object sender, RoutedEventArgs e)
{
    var result = (from s1 in client.GetAllData() orderby s1.CustomerID select s1).ToList();
    bindingList = new BindingList<DataService.Customer>(
                       (IList<DataService.Customer>)result);
    DataContext = bindingList;
    view = CollectionViewSource.GetDefaultView(DataContext);
}
==<end>==============





==<box>===========
程式3
using System;
using System.ComponentModel;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
namespace WpfDataConsumer
{
    public class TrackingContext<T,TUpdate>
    {
        …………….
        public void Initialize(IList<T> objs)
        {
            _states.Clear();
            _update_original = typeof(TUpdate).GetProperty("Original");
            _update_current = typeof(TUpdate).GetProperty("Current");
            _update_state = typeof(TUpdate).GetProperty("State");
            foreach (T item in objs)
            {
                object updateData = Activator.CreateInstance(typeof(TUpdate), false);
                _update_original.SetValue(updateData, CloneObject(item),null);
                _update_current.SetValue(updateData, item, null);
                _update_state.SetValue(updateData, 
                       WpfDataConsumer.DataService.UpdateState.UnChanged, null);
                ((INotifyPropertyChanged)item).PropertyChanged += 
                   new PropertyChangedEventHandler(TrackingContext_PropertyChanged);
                _states.Add(item, (TUpdate)updateData);
            }            
        }
　　　　void TrackingContext_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (_states.ContainsKey((T)sender))
            {
                object o = _states[(T)sender];
                DataService.UpdateState state = 
　　　　　　　　　　　　(DataService.UpdateState)_update_state.GetValue(o, null);
                if (state == WpfDataConsumer.DataService.UpdateState.Insert)
                    return;
                _update_state.SetValue(o, 
　　　　　　　　　　　　WpfDataConsumer.DataService.UpdateState.Update, null);
            }
        }
   }
}
==<end>==============





==<box>===========
程式4
public void UpdateData(UpdateData<Customer>[] updatedData)
{
      NorthwindDataContext context = new NorthwindDataContext();
      try
      {
         foreach (UpdateData<Customer> item in updatedData)
         {
             if (item.State == UpdateState.Insert)
                 context.Customers.InsertOnSubmit((Customer)item.Current);
         }
         foreach (UpdateData<Customer> item in updatedData)
         {
            if (item.State == UpdateState.Update)
                 context.Customers.Attach((Customer)item.Current, (Customer)item.Original);
         }
         foreach (UpdateData<Customer> item in updatedData)
         {
            if (item.State == UpdateState.Delete)
            {
                 context.Customers.Attach((Customer)item.Current);
                 context.Customers.DeleteOnSubmit((Customer)item.Current);
             }
          }
          context.SubmitChanges();
       }
       finally
       {
           context.Dispose();
       }
 }
==<box>===========