ASP.NET Tutorial/ADO.net Database/Async — различия между версиями

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м (1 версия)
 
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Версия 15:30, 26 мая 2010

Executes a database asynchronously but uses code to poll the operation for completion.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" 
    Inherits="Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Polling for Completion</title>
</head>
<body>
   
    <div id="pageContent">
        <form id="form1" runat="server">
            <asp:Button ID="Button1" runat="server" Text="Execute the command" OnClick="Button1_Click" />
            <hr />
            <asp:Label ID="Results" runat="server"></asp:Label>
        </form>
    </div>
</body>
</html>

File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Data.SqlClient;
using System.Web;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        string connString = "Async=true;SERVER=(local);DATABASE=northwind;Trusted_Connection=yes;";
        using (SqlConnection conn = new SqlConnection(connString))
        {
            SqlCommand cmd = new SqlCommand("SELECT lastname,firstname FROM employees", conn);
            conn.Open();
            IAsyncResult iar = cmd.BeginExecuteReader();
            do {
            } while (!iar.IsCompleted);
            SqlDataReader reader = cmd.EndExecuteReader(iar);
            ProcessData(reader);
        }
    }
    protected void ProcessData(SqlDataReader reader)
    {
        StringBuilder sb = new StringBuilder("");
        while (reader.Read())
            sb.AppendFormat("{0}, {1}<br/>", reader[0], reader[1]);
        reader.Close();
        Results.Text = sb.ToString();
    }
}


Fire a database asynchronous operation and then proceeds up to the point where results are required

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" 
    Inherits="Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Non-blocking Commands</title>
</head>
<body>
    <div id="pageContent">
        <form id="form1" runat="server">
            <asp:Button ID="Button1" runat="server" Text="Execute the command" OnClick="Button1_Click" />
            <hr />
            <asp:Label ID="Results" runat="server"></asp:Label>
        </form>
    </div>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
using System.Data.SqlClient;
using System.Web;
using System.Text;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        string connString = "Async=true;SERVER=(local);DATABASE=northwind;Trusted_Connection=yes;";
        using (SqlConnection conn = new SqlConnection(connString))
        {
            SqlCommand cmd = new SqlCommand("SELECT lastname,firstname FROM employees", conn);
            conn.Open();
            IAsyncResult iar = cmd.BeginExecuteReader();
            SqlDataReader reader = (SqlDataReader) cmd.EndExecuteReader(iar);
            ProcessData(reader);
        }
    }
    protected void ProcessData(SqlDataReader reader)
    {
        StringBuilder sb = new StringBuilder("");
        while (reader.Read())
            sb.AppendFormat("{0}, {1}<br/>", reader[0], reader[1]);
        reader.Close();
        Results.Text = sb.ToString();
    }
}
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ADO.net_Database/Async&oldid=2667»