上節(jié)跟大家講了如何用對(duì)象映射工具 eXpress Persistent Objects (XPO) 創(chuàng)建數(shù)據(jù)查詢條件。本節(jié)我們來創(chuàng)建一個(gè)能自動(dòng)保存數(shù)據(jù)到服務(wù)器的ASP.NET應(yīng)用程序，用于查看和編輯用戶詳細(xì)信息。

定義Persistent Object Class

創(chuàng)建一個(gè)新項(xiàng)目后，我們首先要做的就是定義一個(gè)Persistent Object Class，將它作為Customer類，如圖：

 這個(gè)類的FirstName, LastName and Company屬性代表數(shù)據(jù)庫表相應(yīng)字段的值。

using DevExpress.Xpo;

public class Customer : XPObject {
public Customer(Session session) : base(session) {}
public string FirstName;
public string LastName;
public string Company;
}

連接Database Server

接下來將XPO連接到數(shù)據(jù)庫服務(wù)器。方法是創(chuàng)建一個(gè)IDataLayer 對(duì)象，創(chuàng)建數(shù)據(jù)層的代碼必須放在Application_Start事件處理器中（注：這個(gè)處理器在站點(diǎn)的Global.asax模塊中）。

void Application_Start(object sender, EventArgs e) {
// Code that runs on the application startup
// Specify the connection string, which is used to open a database.
// It's supposed that you've already created the Comments database within the App_Data folder.
string conn = DevExpress.Xpo.DB.AccessConnectionProvider.GetConnectionString(
Server.MapPath("~\\App_Data\\Customer.mdb"));
DevExpress.Xpo.Metadata.XPDictionary dict = new DevExpress.Xpo.Metadata.ReflectionDictionary();
// Initialize the XPO dictionary.
dict.GetDataStoreSchema(typeof(Customer).Assembly);
DevExpress.Xpo.XpoDefault.Session = null;
DevExpress.Xpo.DB.IDataStore store =
DevExpress.Xpo.XpoDefault.GetConnectionProvider(conn,
DevExpress.Xpo.DB.AutoCreateOption.DatabaseAndSchema);
DevExpress.Xpo.XpoDefault.DataLayer = new DevExpress.Xpo.ThreadSafeDataLayer(dict, store);
}

使用XpoDataSource組件檢索數(shù)據(jù)

Persistent對(duì)象使用 XpoDataSource 組件檢索數(shù)據(jù)。在聲明了Customer類之后，必須重建方案，從工具箱中將XpoDataSource拖放到頁面上。然后，部署persistent類到Typename屬性：

連接XpoDataSource組件：

Session session1;
protected void Page_Init(object sender, EventArgs e) {
session1 = new Session();
// ...
XpoDataSource1.Session = session1;
}

那么如何顯示數(shù)據(jù)呢？還需要部署XpoDataSource組件。這個(gè)例子中，我們使用了ASPxGridView。下圖展示了如何綁定XpoDataSource到網(wǎng)格：

XpoDataSource綁定到網(wǎng)格后，網(wǎng)格會(huì)為所有的persistent屬性自動(dòng)生成數(shù)據(jù)列。啟動(dòng)數(shù)據(jù)編輯的方式：

最后，添加數(shù)據(jù)到Customer表格中并運(yùn)行項(xiàng)目：

Session session1;
protected void Page_Load(object sender, EventArgs e) {
session1 = new Session();
if (session1.FindObject<Customer>(null) == null) {
Customer cstm = new Customer(session1);
cstm.FirstName = "John";
cstm.LastName = "Doe";
cstm.Company = "Doe Enterprises";
cstm.Save();

cstm = new Customer(session1);
cstm.FirstName = "Sam";
cstm.LastName = "Hill";
cstm.Company = "Hill Corporation";
cstm.Save();
}
XpoDataSource1.Session = session1;
}

最終結(jié)果：

用戶可以查看并編輯網(wǎng)格中的數(shù)據(jù)，最重要的是，你無需編寫代碼去保存這些數(shù)據(jù)。一旦表格發(fā)生變化，它就會(huì)自動(dòng)保存到服務(wù)器上。