방법: 백그라운드에서 파일 다운로드

파일 다운로드는 일반적으로 수행되는 작업이며 시간이 많이 걸릴 수도 있는 작업이므로 별개의 스레드에서 실행하는 것이 유용합니다. BackgroundWorker 구성 요소를 사용하면 매우 적은 양의 코드로 이 작업을 수행할 수 있습니다.

예제

다음 코드 예제에서는 BackgroundWorker 구성 요소를 사용하여 URL에서 XML 파일을 로드하는 방법을 보여 줍니다. 사용자가 다운로드 단추를 클릭하면 Click 이벤트 처리기가 BackgroundWorker 구성 요소의 RunWorkerAsync 메서드를 호출하여 다운로드 작업을 시작합니다. 이 단추는 다운로드하는 동안 비활성화되었다가 다운로드가 완료되면 활성화됩니다. MessageBox에는 파일의 내용이 표시됩니다.

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Drawing
Imports System.Threading
Imports System.Windows.Forms
Imports System.Xml

Public Class Form1
    Inherits Form

    Private WithEvents downloadButton As Button
    Private WithEvents progressBar1 As ProgressBar
    Private WithEvents backgroundWorker1 As BackgroundWorker
    Private document As XmlDocument = Nothing

    Public Sub New()
        InitializeComponent()
        Me.backgroundWorker1 = New System.ComponentModel.BackgroundWorker()
    End Sub

    Private Sub downloadButton_Click( _
        ByVal sender As Object, _
        ByVal e As EventArgs) _
        Handles downloadButton.Click

        ' Start the download operation in the background.
        Me.backgroundWorker1.RunWorkerAsync()

        ' Disable the button for the duration of the download.
        Me.downloadButton.Enabled = False

        ' Once you have started the background thread you 
        ' can exit the handler and the application will 
        ' wait until the RunWorkerCompleted event is raised.

        ' If you want to do something else in the main thread,
        ' such as update a progress bar, you can do so in a loop 
        ' while checking IsBusy to see if the background task is
        ' still running.
        While Me.backgroundWorker1.IsBusy
            progressBar1.Increment(1)
            ' Keep UI messages moving, so the form remains 
            ' responsive during the asynchronous operation.
            Application.DoEvents()
        End While
    End Sub

    Private Sub backgroundWorker1_DoWork( _
        ByVal sender As Object, _
        ByVal e As DoWorkEventArgs) _
        Handles backgroundWorker1.DoWork

        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);
    End Sub

    Private Sub backgroundWorker1_RunWorkerCompleted( _
        ByVal sender As Object, _
        ByVal e As RunWorkerCompletedEventArgs) _
        Handles backgroundWorker1.RunWorkerCompleted

        ' Set progress bar to 100% in case it isn't already there.
        progressBar1.Value = 100

        If e.Error Is Nothing Then
            MessageBox.Show(document.InnerXml, "Download Complete")
        Else
            MessageBox.Show("Failed to download file", "Download failed", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End If

        ' Enable the download button and reset the progress bar.
        Me.downloadButton.Enabled = True
        progressBar1.Value = 0
    End Sub

#Region "Windows Form Designer generated code"
    ' <summary>
    ' Required designer variable.
    ' </summary>
    Private components As System.ComponentModel.IContainer = Nothing

    ' <summary>
    ' Clean up any resources being used.
    ' </summary>
    ' <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing AndAlso (components IsNot Nothing) Then
            components.Dispose()
        End If
        MyBase.Dispose(disposing)
    End Sub

    ' <summary>
    ' Required method for Designer support - do not modify
    ' the contents of this method with the code editor.
    ' </summary>
    Private Sub InitializeComponent()
        Me.downloadButton = New System.Windows.Forms.Button
        Me.progressBar1 = New System.Windows.Forms.ProgressBar
        Me.SuspendLayout()
        '
        'downloadButton
        '
        Me.downloadButton.Location = New System.Drawing.Point(12, 12)
        Me.downloadButton.Name = "downloadButton"
        Me.downloadButton.Size = New System.Drawing.Size(100, 23)
        Me.downloadButton.TabIndex = 0
        Me.downloadButton.Text = "Download file"
        Me.downloadButton.UseVisualStyleBackColor = True
        '
        'progressBar1
        '
        Me.progressBar1.Location = New System.Drawing.Point(12, 50)
        Me.progressBar1.Name = "progressBar1"
        Me.progressBar1.Size = New System.Drawing.Size(100, 26)
        Me.progressBar1.TabIndex = 1
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(136, 104)
        Me.Controls.Add(Me.downloadButton)
        Me.Controls.Add(Me.progressBar1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region
End Class


Public Class Program

    ' <summary>
    ' The main entry point for the application.
    ' </summary>
    <STAThread()> _
    Shared Sub Main()
        Application.EnableVisualStyles()
        Application.Run(New Form1())
    End Sub
End Class

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 downloadButton;
    private ProgressBar progressBar1;
    private XmlDocument document = null;

    public Form1()
    {
        InitializeComponent();

        // Instantiate BackgroundWorker and attach handlers to its
        // DowWork and RunWorkerCompleted events.
        backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
        backgroundWorker1.DoWork += new System.ComponentModel.DoWorkEventHandler(this.backgroundWorker1_DoWork);
        backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);
    }

    private void downloadButton_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.downloadButton.Enabled = false;

        // Once you have started the background thread you 
        // can exit the handler and the application will 
        // wait until the RunWorkerCompleted event is raised.

        // Or if you want to do something else in the main thread,
        // such as update a progress bar, you can do so in a loop 
        // while checking IsBusy to see if the background task is
        // still running.

        while (this.backgroundWorker1.IsBusy)
        {
            progressBar1.Increment(1);
            // Keep UI messages moving, so the form remains 
            // responsive during the asynchronous operation.
            Application.DoEvents();
        }
    }

    private void backgroundWorker1_DoWork(
        object sender,
        DoWorkEventArgs e)
    {
        document = new XmlDocument();

        // Uncomment the following line to
        // simulate a noticeable latency.
        //Thread.Sleep(5000);

        // Replace this file name with a valid file name.
        document.Load(@"http://www.tailspintoys.com/sample.xml");
    }

    private void backgroundWorker1_RunWorkerCompleted(
        object sender,
        RunWorkerCompletedEventArgs e)
    {
        // Set progress bar to 100% in case it's not already there.
        progressBar1.Value = 100;

        if (e.Error == null)
        {
            MessageBox.Show(document.InnerXml, "Download Complete");
        }
        else
        {
            MessageBox.Show(
                "Failed to download file",
                "Download failed",
                MessageBoxButtons.OK,
                MessageBoxIcon.Error);
        }

        // Enable the download button and reset the progress bar.
        this.downloadButton.Enabled = true;
        progressBar1.Value = 0;
    }

    #region Windows Form Designer generated code

    /// <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);
    }

    /// <summary>
    /// Required method for Designer support
    /// </summary>
    private void InitializeComponent()
    {
        this.downloadButton = new System.Windows.Forms.Button();
        this.progressBar1 = new System.Windows.Forms.ProgressBar();
        this.SuspendLayout();
        // 
        // downloadButton
        // 
        this.downloadButton.Location = new System.Drawing.Point(12, 12);
        this.downloadButton.Name = "downloadButton";
        this.downloadButton.Size = new System.Drawing.Size(100, 23);
        this.downloadButton.TabIndex = 0;
        this.downloadButton.Text = "Download file";
        this.downloadButton.UseVisualStyleBackColor = true;
        this.downloadButton.Click += new System.EventHandler(this.downloadButton_Click);
        // 
        // progressBar1
        // 
        this.progressBar1.Location = new System.Drawing.Point(12, 50);
        this.progressBar1.Name = "progressBar1";
        this.progressBar1.Size = new System.Drawing.Size(100, 26);
        this.progressBar1.TabIndex = 1;
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(133, 104);
        this.Controls.Add(this.progressBar1);
        this.Controls.Add(this.downloadButton);
        this.Name = "Form1";
        this.Text = "Form1";
        this.ResumeLayout(false);

    }

    #endregion
}

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}

파일 다운로드

파일은 BackgroundWorker 구성 요소의 작업자 스레드에서 다운로드되며, 이 스레드에서는 DoWork 이벤트 처리기가 실행됩니다. 이 스레드는 코드에서 RunWorkerAsync 메서드가 호출될 때 시작됩니다.

Private Sub backgroundWorker1_DoWork( _
    ByVal sender As Object, _
    ByVal e As DoWorkEventArgs) _
    Handles backgroundWorker1.DoWork

    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);
End Sub

private void backgroundWorker1_DoWork(
    object sender,
    DoWorkEventArgs e)
{
    document = new XmlDocument();

    // Uncomment the following line to
    // simulate a noticeable latency.
    //Thread.Sleep(5000);

    // Replace this file name with a valid file name.
    document.Load(@"http://www.tailspintoys.com/sample.xml");
}

BackgroundWorker 완료 시까지 대기

downloadButton_Click 이벤트 처리기는 BackgroundWorker 구성 요소에서 비동기 작업이 완료될 때까지 대기하는 방법을 보여 줍니다.

백그라운드 스레드가 완료될 때까지 기다리는 동안 응용 프로그램이 이벤트에만 응답하고 주 스레드에서 아무 작업도 수행하지 않도록 하려면 처리기를 종료하면 됩니다.

주 스레드의 작업을 계속 수행하려면 IsBusy 속성을 사용하여 BackgroundWorker 스레드가 계속 실행 중인지 확인합니다. 이 예제에서는 다운로드가 진행되는 동안 진행률 표시줄이 업데이트됩니다. 이 경우 Application.DoEvents 메서드를 호출하여 UI 응답 기능을 유지해야 합니다.

Private Sub downloadButton_Click( _
    ByVal sender As Object, _
    ByVal e As EventArgs) _
    Handles downloadButton.Click

    ' Start the download operation in the background.
    Me.backgroundWorker1.RunWorkerAsync()

    ' Disable the button for the duration of the download.
    Me.downloadButton.Enabled = False

    ' Once you have started the background thread you 
    ' can exit the handler and the application will 
    ' wait until the RunWorkerCompleted event is raised.

    ' If you want to do something else in the main thread,
    ' such as update a progress bar, you can do so in a loop 
    ' while checking IsBusy to see if the background task is
    ' still running.
    While Me.backgroundWorker1.IsBusy
        progressBar1.Increment(1)
        ' Keep UI messages moving, so the form remains 
        ' responsive during the asynchronous operation.
        Application.DoEvents()
    End While
End Sub

private void downloadButton_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.downloadButton.Enabled = false;

    // Once you have started the background thread you 
    // can exit the handler and the application will 
    // wait until the RunWorkerCompleted event is raised.

    // Or if you want to do something else in the main thread,
    // such as update a progress bar, you can do so in a loop 
    // while checking IsBusy to see if the background task is
    // still running.

    while (this.backgroundWorker1.IsBusy)
    {
        progressBar1.Increment(1);
        // Keep UI messages moving, so the form remains 
        // responsive during the asynchronous operation.
        Application.DoEvents();
    }
}

결과 표시

backgroundWorker1_RunWorkerCompleted 메서드는 RunWorkerCompleted 이벤트를 처리하며 백그라운드 작업이 완료되었을 때 호출됩니다. 이 메서드는 먼저 AsyncCompletedEventArgs.Error 속성을 검사하여 AsyncCompletedEventArgs.Error가 null이면 파일 내용을 표시합니다. 그런 다음 다운로드가 시작될 때 비활성화한 다운로드 단추를 활성화하고 진행률 표시줄을 다시 설정합니다.

Private Sub backgroundWorker1_RunWorkerCompleted( _
    ByVal sender As Object, _
    ByVal e As RunWorkerCompletedEventArgs) _
    Handles backgroundWorker1.RunWorkerCompleted

    ' Set progress bar to 100% in case it isn't already there.
    progressBar1.Value = 100

    If e.Error Is Nothing Then
        MessageBox.Show(document.InnerXml, "Download Complete")
    Else
        MessageBox.Show("Failed to download file", "Download failed", MessageBoxButtons.OK, MessageBoxIcon.Error)
    End If

    ' Enable the download button and reset the progress bar.
    Me.downloadButton.Enabled = True
    progressBar1.Value = 0
End Sub

private void backgroundWorker1_RunWorkerCompleted(
    object sender,
    RunWorkerCompletedEventArgs e)
{
    // Set progress bar to 100% in case it's not already there.
    progressBar1.Value = 100;

    if (e.Error == null)
    {
        MessageBox.Show(document.InnerXml, "Download Complete");
    }
    else
    {
        MessageBox.Show(
            "Failed to download file",
            "Download failed",
            MessageBoxButtons.OK,
            MessageBoxIcon.Error);
    }

    // Enable the download button and reset the progress bar.
    this.downloadButton.Enabled = true;
    progressBar1.Value = 0;
}

코드 컴파일

이 예제에는 다음 사항이 필요합니다.

• System.Drawing, System.Windows.Forms 및 System.Xml 어셈블리에 대한 참조

Visual Basic 또는 Visual C#의 명령줄에서 이 예제를 빌드하는 방법에 대한 자세한 내용은 명령줄에서 빌드(Visual Basic) 또는 csc.exe를 사용한 명령줄 빌드를 참조하십시오. Visual Studio에서 코드를 새 프로젝트에 붙여넣어 이 예제를 빌드할 수도 있습니다. 자세한 내용은 다음을 참조하십시오. 방법: Visual Studio를 사용하여 전체 Windows Forms 코드 예제 컴파일 및 실행 및 방법: Visual Studio를 사용하여 전체 Windows Forms 코드 예제 컴파일 및 실행 및 방법: Visual Studio를 사용하여 전체 Windows Forms 코드 예제 컴파일 및 실행 및 방법: Visual Studio를 사용하여 전체 Windows Forms 코드 예제 컴파일 및 실행 및 방법: Visual Studio를 사용하여 전체 Windows Forms 코드 예제 컴파일 및 실행.

강력한 프로그래밍

DoWork 이벤트 처리기의 영향을 받을 수 있는 RunWorkerCompletedEventArgs.Result 속성이나 다른 모든 개체에 액세스하기 전에 항상 RunWorkerCompleted 이벤트 처리기의 AsyncCompletedEventArgs.Error 속성을 확인합니다.

참고 항목

작업

방법: 백그라운드에서 작업 실행

방법: 백그라운드 작업을 사용하는 폼 구현

참조

BackgroundWorker