原创 ADO.NET2.0 异步处理的三种方式－函数回调法

下面的代码用内嵌sql语句方式通过调用BeginExecuteReader取出前五条数据，并且把callback的代理传给这个方法。不需要其他的处理，当这个异步调用结束时回调函数将被触发，并且取出结果集显示在屏幕上。

<%@ Page Language=”C#” %>

<%@ Import Namespace=”System.Data” %>

<%@ Import Namespace=”System.Data.SqlClient” %>

<%@ Import Namespace=”System.Configuration” %>

<script runat=”server”>

protected void Page_Load(object sender, EventArgs e)

{

SqlConnection DBCon;

SqlCommand Command = new SqlCommand();

SqlAsyncResult ASyncResult;

DBCon = new SqlConnection();

Command = new SqlCommand();

DBCon.ConnectionString =

ConfigurationManager.ConnectionStrings[“DSN_NorthWind”].ConnectionString;

// Selecting top 5 records from the Orders table

Command.CommandText =

“ Orders.RequiredDate, Orders.ShippedDate “ +

“ FROM Orders, Customers “ +

“ WHERE Orders.CustomerID = Customers.CustomerID “ +

“ ORDER BY Customers.CompanyName, Customers.ContactName “;

Command.CommandType = CommandType.Text;

Command.Connection = DBCon;

DBCon.Open();

// Starting the asynchronous processing

AsyncResult = Command.BeginExecuteReader(new AsyncCallback(CBMethod),

CommandBehavior.CloseConnection);

}

public void CBMethod(SQLAsyncResult ar)

{

SqlDataReader OrdersReader;

// Retrieving result from the asynchronous process

OrdersReader = ar.EndExecuteReader(ar);

// Displaying result on the screen

gvOrders.DataSource = OrdersReader;

gvOrders.DataBind();

}

</script>