.NET 4.0 - Winform Control - DataGridView 数据绑定(ADO.NET Data Service)

ADO.NET Data Service 是一种基于REST架构的WCF + EF + OData(协议)的服务，.NET 客户端可以像引用其他WCF服务一样，添加services reference获得很好的客户端支持。客户端代理主要由 DataServiceContext 和 Entities 组成，因此客户端可以用类似 Linq2Entites 的方法获取 Data Service 的数据，底层框架将 Linq 语句转成 DataServiceQuery 再转成 HttpWebRequest 发起对服务的请求，并对返回的 HttpWebResponse 解析反序列化成实体。对 Data Service Client Library 的用户而言，事情很简单，执行效率也相应提高。但是其他语言的用户可就遭罪了，得自己拼接大量的字符串。其他详细参看：http://www.rainsts.net/article.asp?id=809 (雨痕的blog)。本篇文章，主要针对客户端调用来了解 Data Service 的特点。
 
1. 服务端的创建：
(1) 创建 WCF Application Service 工程
(2) 添加 ADO.NET Entity Data Model
(3) 删除既有的 .svc 文件，添加一个 AppFabric-enabled WCF Data Service
     (该模板可以通过 Extension Manager 在线下载) 
 


(4) 修改刚才添加的 DataService 类为如下：
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
public class NorthwindDataService : DataService<NORTHWNDEntities>
{
// This method is called only once to initialize service-wide policies.
public static void InitializeService(DataServiceConfiguration config)
{
// TODO: set rules to indicate which entity sets and service operations are visible, updatable, etc.
// Examples:
// config.SetEntitySetAccessRule("MyEntityset", EntitySetRights.AllRead);
// config.SetServiceOperationAccessRule("MyServiceOperation", ServiceOperationRights.All);
config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
config.SetEntitySetAccessRule("*", EntitySetRights.All);
RouteTable.Routes.Add(
new ServiceRoute("NorthwindDataService", new DataServiceHostFactory(), typeof(NorthwindDataService)));

}
}
2. 客户端添加 Service Reference



3. 要完成的任务：实现下面3个表的连动绑定并实现Update处理。



简单说明：
(1)  客户端每次访问 Data Service 都是调用一次 Http Request，默认使用的是 Atom XML 格式。
       (Execute，LoadProperty, SaveChanges等方法)
(2)  DataServiceContext 会将查询过的数据在客户端缓存，并对缓存的数据进行 State Tracing。
       直到 DataServiceContext 被销毁。可以通过 DataServiceContext.Entities 获得跟踪实体的实例。
(3)  因为在客户端缓存了数据，所以存在普遍的并发风险。另外查询时，会根据 MergeOptions 来更新客户端缓存。
(4)  Navigation Property 在客户端的实体里不支持，关联数据需要手动查询，可以利用(LoadProperty方法)
      提交的时候可以用: SetLink, AddLink, DeleteLink 进行关联。
(5)  将数据提交到服务端需要先对应调用下面的方法：
      添加 -- AddToXXX 或者 AddObject(string entitySetName, object entity);
      更新 -- UpdateObject(object entity);
      删除 -- DeleteObject(object entity);
      最后调用 SaveChanges() 方法
(6)  Linq2DataService 返回的是 DataServiceQuery<T> (封装的是请求的Uri)，
      需要调用Execute(同步)或者BeginExecute(异步)才能获取结果。
(7) 每一个实体都对应服务端一个Identity(uri)
 
客户端UI：



根据上面说明的第(5)条，数据提交之前必须调用UpdateObject方法，因此可以利用 BindingSource 的ListChanged 事件即时调用UpdateObject，等"Update"按钮事件处理方法中直接调用 SaveChanges 方法就可以了。 
 
客户端代码：详细看注释
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;
using System.Data.Services.Client;
using System.Collections.ObjectModel;
using System.Net;

namespace WcfDataServiceClient
{
public partial class DataBindDemo : Form
{

public DataBindDemo()
{
InitializeComponent();
}

private NorthwindDataSvc.NORTHWNDEntities northwind;

private void Form1_Load(object sender, EventArgs e)
{
// 将地址设置到TcpTracer监听的20000端口上,TcpTracer将转发至服务的真实IP:58960
var svcUri = new Uri("http://localhost:20000/NorthwindDataService.svc");
northwind = new NorthwindDataSvc.NORTHWNDEntities(svcUri);
// 绑定数据,最初只有customers
BindData();

// 为了避免绑定时触发 SelectedIndexChanged 事件，
// SelectedIndexChanged 事件的绑定放在Customers数据加载之后
// 绑定customers的选择变更事件，加载orders
lstCustomer.SelectedIndexChanged += new EventHandler(lstCustomer_SelectedIndexChanged);
// 绑定orders的选择变更事件，加载order_details
dgvOrders.SelectionChanged += new EventHandler(dgvOrders_SelectionChanged);

// 绑定各BindingSource的ListChanged事件，修改缓存状态
customerBindingSource.ListChanged += new ListChangedEventHandler(UpdateEntity);

// 触发一次SelectedIndexChanged, 加载orders和order_detailss
lstCustomer.SelectedIndex = -1;
lstCustomer.SelectedIndex = 0;
}

private void UpdateEntity(object sender, ListChangedEventArgs e)
{
if (e.ListChangedType != ListChangedType.ItemChanged) return;
// 从BindingSource中获取当前变更的数据
var data = ((BindingSource)sender).Current;
// 告知本地缓存该数据发生变更
northwind.UpdateObject(data);
}

private void lstCustomer_SelectedIndexChanged(object sender, EventArgs e)
{
var customer = lstCustomer.SelectedItem as NorthwindDataSvc.Customer;
if (customer == null) return;
orderBindingSource.ListChanged -= UpdateEntity;
// 这里DataService里没有Navigation Property，
// customer.Orders(DataServiceCollection<T>)并没有数据
// 在SaveChanges之前都使用客户端数据
northwind.MergeOption = MergeOption.PreserveChanges;
northwind.LoadProperty(customer, "Orders");
orderBindingSource.DataSource = customer.Orders;
dgvOrders.DataSource = orderBindingSource;
orderBindingSource.ListChanged += UpdateEntity;
}

private void dgvOrders_SelectionChanged(object sender, EventArgs e)
{
if (dgvOrders.SelectedRows.Count <= 0) return;
orderDetailBindingSource.ListChanged -= UpdateEntity;
var order = dgvOrders.BindingContext[dgvOrders.DataSource].Current as NorthwindDataSvc.Order;
northwind.MergeOption = MergeOption.PreserveChanges;
northwind.LoadProperty(order, "Order_Details");
orderDetailBindingSource.DataSource = order.Order_Details.ToList();
dgvOrderDetails.DataSource = orderDetailBindingSource;
orderDetailBindingSource.ListChanged += UpdateEntity;
}

private void BindData()
{
customerBindingSource.DataSource = northwind.Customers.Execute().ToList();
lstCustomer.DataSource = customerBindingSource;
lstCustomer.ValueMember = "ContactName";
lstCustomer.DisplayMember = "ContactName";

txtName.DataBindings.Add("Text", customerBindingSource, "ContactName");
txtContactTitle.DataBindings.Add("Text", customerBindingSource, "ContactTitle");
txtAddress.DataBindings.Add("Text", customerBindingSource, "Address");
txtCity.DataBindings.Add("Text", customerBindingSource, "City");
txtRegion.DataBindings.Add("Text", customerBindingSource, "Region");
txtPostalCode.DataBindings.Add("Text", customerBindingSource, "PostalCode");
txtPhone.DataBindings.Add("Text", customerBindingSource, "Phone");
txtFax.DataBindings.Add("Text", customerBindingSource, "Fax");
txtCountry.DataBindings.Add("Text", customerBindingSource, "Country");
}

private void btnUpdate_Click(object sender, EventArgs e)
{
try
{
// 获得DataServiceContext中跟踪的Entities中的变更过的数据
var changedEntities = northwind.Entities.
Where(et => et.State != EntityStates.Unchanged).ToList();
string log = string.Format("Have [{0}] datas been changed.\n", changedEntities.Count);
foreach (var entity in changedEntities)
log += entity.ServerTypeName + ":" + entity.State + "\n";
MessageBox.Show(log);
// 如果有变更
if (changedEntities.Count > 0)
{
// 批量提交数据(即数据在一个Request内提交)
var resp = northwind.SaveChanges(SaveChangesOptions.Batch);
MessageBox.Show(((HttpStatusCode)resp.BatchStatusCode).ToString());
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
try
{
// 获得DataServiceContext中跟踪的Entities中的变更过的数据
var changedEntities = northwind.Entities.Where(et => et.State != EntityStates.Unchanged);
// 指定更新行为：如果本地数据不一致则用服务端数据覆盖
northwind.MergeOption = MergeOption.OverwriteChanges;
foreach (var entity in changedEntities)
{
// 无论请求成功还是失败，重新查询把跟踪对象的State改为Unchanged.
northwind.Execute<object>(new Uri(entity.Identity)).ToList();
}
}
catch
{
}
}
}

private void btnFirst_Click(object sender, EventArgs e)
{
customerBindingSource.MoveFirst();
}

private void btnPre_Click(object sender, EventArgs e)
{
customerBindingSource.MovePrevious();
}

private void btnNext_Click(object sender, EventArgs e)
{
customerBindingSource.MoveNext();
}

private void btnLast_Click(object sender, EventArgs e)
{
customerBindingSource.MoveLast();
}
}
}
执行成功的话，将会获得 Accept 的 ResponseStatus