asp.net BackgroundWorker之在后臺(tái)下載文件
2024-07-10 12:41:35
供稿：網(wǎng)友
示例：
下面的代碼示例演示如何使用 BackgroundWorker 組件從 URL 加載 XML 文件。用戶單擊“下載”按鈕時(shí)，Click 事件處理程序?qū)⒄{(diào)用 BackgroundWorker 組件的 RunWorkerAsync 方法來啟動(dòng)下載操作。在下載過程中，將禁用該按鈕，然后在下載完成后再啟用該按鈕。MessageBox 將顯示文件的內(nèi)容。
代碼如下:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Threading;
using System.Windows.Forms;
using System.Xml;
public class Form1 : Form
{
private BackgroundWorker backgroundWorker1;
private Button dowloadButton;
private XmlDocument document = null;
public Form1()
{
InitializeComponent();
}
private void dowloadButton_Click(object sender, EventArgs e)
{
// Start the download operation in the background.
this.backgroundWorker1.RunWorkerAsync();
// Disable the button for the duration of the download.
this.dowloadButton.Enabled = false;
// Wait for the BackgroundWorker to finish the download.
while (this.backgroundWorker1.IsBusy)
{
// Keep UI messages moving, so the form remains
// responsive during the asynchronous operation.
Application.DoEvents();
}
// The download is done, so enable the button.
this.dowloadButton.Enabled = true;
}
private void backgroundWorker1_DoWork(
object sender,
DoWorkEventArgs e)
{
document = new XmlDocument();
// Replace this file name with a valid file name.
document.Load(@"http://www.tailspintoys.com/sample.xml");
// Uncomment the following line to
// simulate a noticeable latency.
//Thread.Sleep(5000);
}
private void backgroundWorker1_RunWorkerCompleted(
object sender,
RunWorkerCompletedEventArgs e)
{
if (e.Error == null)
{
MessageBox.Show(document.InnerXml, "Download Complete");
}
else
{
MessageBox.Show(
"Failed to download file",
"Download failed",
MessageBoxButtons.OK,
MessageBoxIcon.Error );
}
}
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.IContainer components = null;
/// <summary>
/// Clean up any resources being used.
/// </summary>
/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
this.dowloadButton = new System.Windows.Forms.Button();
this.SuspendLayout();
