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;            s
         tring 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 = 0;            
                this.proBarDownLoad.Maximum = (int)e.TotalBytesToReceive;           
                this.proBarDownLoad.Value = (int)e.BytesReceived;           
                this.lblPercent.Text = e.ProgressPercentage + "%";
        }
    }
}

测试