#眉標=LINQ	
#副標=剖析LINQ運作機制（5）
#大標=實做完整功能的單檔編輯應用程式
#作者=文圖／黃忠成


==<box>===========
程式1
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace SingleEdit
{
    public partial class Form1 : Form
    {
        NorthwindDataContext _context = new NorthwindDataContext();

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            bindingSource1.DataSource = _context.Customers;
        }
    }
}
==<end>==============




==<box>===========
程式2
private void toolStripButton1_Click(object sender, EventArgs e)
{
     bindingSource1.EndEdit();
     _context.SubmitChanges();
}==<end>==============



==<box>===========
程式3
private void toolStripButton2_Click(object sender, EventArgs e)
{
    bindingSource1.CancelEdit();
}==<end>==============




==<box>===========
程式4
private void toolStripButton2_Click(object sender, EventArgs e)
{
      bindingSource1.CancelEdit();            
　　　_context.Refresh(
System.Data.Linq.RefreshMode.OverwriteCurrentValues, bindingSource1.Current);
       bindingSource1.ResetCurrentItem();
}==<end>==============




==<box>===========
程式5
using System.Reflection;
....................
private void toolStripButton2_Click(object sender, EventArgs e)
{
       bindingSource1.CancelEdit();
       object original = ((ITable)bindingSource1.DataSource).GetOriginalEntityState(
　　　　　　　　　　　　bindingSource1.Current);
       object current = bindingSource1.Current;
       foreach (PropertyInfo pi in current.GetType().GetProperties())
            pi.SetValue(current, pi.GetValue(original,null),null);
       bindingSource1.ResetCurrentItem();
}==<end>==============



==小技巧	<box>===========
若以SQL Server Profiler觀察，會發現每次SubmitChanges函式呼叫時，LINQ To SQL都會送出一段指令，要避免這種無謂的網路通訊，可以藉助DataContext的GetChangeSet函式，判斷其Deletes、Inserts、Updates、三個屬性的Count屬性，再決定是否呼叫SubmitChanges函式。
==<end>==============