在客户端获得linq to sql 的changeset

用法

  public   partial   class  Form1 : Form
     {
        public Form1()
        {
            InitializeComponent();
        }
        private ObjectSet<MachineCategory> objectSet;
        private void button1_Click(object sender, EventArgs e)
        {
            using (NmisDataContext db = new NmisDataContext())
            {
                objectSet = new ObjectSet<MachineCategory>(db.MachineCategories.ToList());
                bindingSource1.DataSource = objectSet;
                dataGridView1.DataSource = bindingSource1;
            }

        }

        private void button2_Click(object sender, EventArgs e)
        {
            MessageBox.Show(objectSet.Context.GetModified<MachineCategory>().Current.Count.ToString());
            MessageBox.Show(objectSet.Context.GetDeleted<MachineCategory>().Current.Count.ToString());

            MessageBox.Show(objectSet.Context.GetInserted<MachineCategory>().Count.ToString());

        }
    }

1. 自定义的从IBindingList继承的类

public   class  ObjectSet < TEntity >  : System.ComponentModel.BindingList < TEntity >   where  TEntity : class
     {

        private ClientSideContext context;
        public ClientSideContext Context
        {
            get { return context; }
            
        }
        public ObjectSet(IList<TEntity> entities):base(entities)
        {
            context = new ClientSideContext();
            context.AttachAll<TEntity>(entities);
        
            
        }

        protected override void InsertItem(int index, TEntity item)
        {
            base.InsertItem(index, item);
            Context.Add<TEntity>(item);
        }
      
       
        
      
        protected override void RemoveItem(int index)
        {
           
            Context.Remove<TEntity>(this[index]);
            base.RemoveItem(index);
        }
      

2. 老外blog上的ClientSideDataContext

  public   class  ClientSideContext : IDisposable
     {
        public class StateEntries<T>
        {
            public List<T> Originals { get; set; }
            public List<T> Current { get; set; }
        }
        public ClientSideContext()
        {
            ctx = new DataContext("", new AttributeMappingSource());
            ctx.DeferredLoadingEnabled = false;
        }
        public void AttachAll<T>(IEnumerable<T> entities) where T : class
        {
            ctx.GetTable<T>().AttachAll(entities);
        }
        public void Attach<T>(T t) where T : class
        {
            ctx.GetTable<T>().Attach(t);
        }
        public void Remove<T>(T t) where T : class
        {
            ctx.GetTable<T>().DeleteOnSubmit(t);
        }
        public void Add<T>(T t) where T : class
        {
            ctx.GetTable<T>().InsertOnSubmit(t);
        }
        public List<T> GetInserted<T>() where T : class
        {
            return (GetChangeEntries<T>(ch => ch.Inserts));
        }
        public StateEntries<T> GetDeleted<T>() where T : class
        {
            return (GetStateEntries<T>(ch => ch.Deletes));
        }
        private StateEntries<T> GetStateEntries<T>(
        Func<ChangeSet, IEnumerable<Object>> entry) where T : class
        {
            List<T> current = GetChangeEntries<T>(entry);
            List<T> originals = GetOriginals<T>(current);
            return (new StateEntries<T>()
            {
                Originals = originals,
                Current = current
            });
        }
        public StateEntries<T> GetModified<T>() where T : class
        {
            return (GetStateEntries<T>(ch => ch.Updates));
        }
        public void Dispose()
        {
            ctx.Dispose();
        }
        List<T> GetChangeEntries<T>(
        Func<ChangeSet, IEnumerable<Object>> selectMember) where T : class
        {
            var query = from o in selectMember(ctx.GetChangeSet())
                        where ((o as T) != null)
                        select (T)o;
            return (new List<T>(query));
        }
        List<T> GetOriginals<T>(List<T> current) where T : class
        {
            List<T> originals = new List<T>(
            from c in current
            select ctx.GetTable<T>().GetOriginalEntityState(c));
            return (originals);
        }
        private DataContext ctx;
    }