[c#]WebClient异步下载文件并显示进度

摘要

在项目开发中经常会用到下载文件，这里使用winform实现了一个带进度条的例子。

一个例子

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.IO;

using System.Linq;

using System.Net;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace Wolfy.DownLoad

{

    public partial class MainFrm : Form

    {

        private string _saveDir;

        public MainFrm()

        {

            InitializeComponent();

            _saveDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "download");

        }

        private void MainFrm_Load(object sender, EventArgs e)

        {

            if (!Directory.Exists(_saveDir))

            {

                Directory.CreateDirectory(_saveDir);

            }

        }

        private void btnDownLoad_Click(object sender, EventArgs e)

        {

            string imageUrl = "http://image.3761.com/nvxing/2016022921/2016022921382152113.jpg";

            string fileExt = Path.GetExtension(imageUrl);

            string fileNewName = Guid.NewGuid() + fileExt;

            bool isDownLoad = false;

            string filePath = Path.Combine(_saveDir, fileNewName);

            if (File.Exists(filePath))

            {

                isDownLoad = true;

            }

            var file = new FileMessage

               {

                   FileName = fileNewName,

                   RelativeUrl = "nvxing/2016022921/2016022921382152113.jpg",

                   Url = imageUrl,

                   IsDownLoad = isDownLoad,

                   SavePath = filePath

               };

            if (!file.IsDownLoad)

            {

                string fileDirPath = Path.GetDirectoryName(file.SavePath);

                if (!Directory.Exists(fileDirPath))

                {

                    Directory.CreateDirectory(fileDirPath);

                }

                try

                {

                    WebClient client = new WebClient();

                    client.DownloadFileCompleted += client_DownloadFileCompleted;

                    client.DownloadProgressChanged += client_DownloadProgressChanged;

                    client.DownloadFileAsync(new Uri(file.Url), file.SavePath, file.FileName);

                }

                catch

                {

                }

            }

        }

        void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)

        {

            if (e.UserState != null)

            {

                this.lblMessage.Text = e.UserState.ToString() + ",下载完成";

            }

        }

        void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)

        {

            this.proBarDownLoad.Minimum = ;

            this.proBarDownLoad.Maximum = (int)e.TotalBytesToReceive;

            this.proBarDownLoad.Value = (int)e.BytesReceived;

            this.lblPercent.Text = e.ProgressPercentage + "%";

        }

    }

}

测试