C# Winform下载文件并显示进度条的实现代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WinShowDown
{
 public partial class FrmMain : Form
 {
  public FrmMain()
  {
   InitializeComponent();
  }

  private void btnDown_Click(object sender, EventArgs e)
  {
   DownloadFile("http://localhost:1928/WebServer/downloader/123.rar", @"C:\123.rar", progressBar1, label1);
  }
  /// <summary>  
  /// c#,.net 下载文件  
  /// </summary>  
  /// <param name="URL">下载文件地址</param>  
  /// 
  /// <param name="Filename">下载后的存放地址</param>  
  /// <param name="Prog">用于显示的进度条</param>  
  /// 
  public void DownloadFile(string URL, string filename, System.Windows.Forms.ProgressBar prog, System.Windows.Forms.Label label1)
  {
   float percent = 0;
   try
   {
    System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL);
    System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)Myrq.GetResponse();
    long totalBytes = myrp.ContentLength;
    if (prog != null)
    {
     prog.Maximum = (int)totalBytes;
    }
    System.IO.Stream st = myrp.GetResponseStream();
    System.IO.Stream so = new System.IO.FileStream(filename, System.IO.FileMode.Create);
    long totalDownloadedByte = 0;
    byte[] by = new byte[1024];
    int osize = st.Read(by, 0, (int)by.Length);
    while (osize > 0)
    {
     totalDownloadedByte = osize + totalDownloadedByte;
     System.Windows.Forms.Application.DoEvents();
     so.Write(by, 0, osize);
     if (prog != null)
     {
      prog.Value = (int)totalDownloadedByte;
     }
     osize = st.Read(by, 0, (int)by.Length);

     percent = (float)totalDownloadedByte / (float)totalBytes * 100;
     label1.Text = "当前补丁下载进度" + percent.ToString() + "%";
     System.Windows.Forms.Application.DoEvents(); //必须加注这句代码，否则label1将因为循环执行太快而来不及显示信息
    }
    so.Close();
    st.Close();
   }
   catch (System.Exception)
   {
    throw;
   }
  }
 }
}

/// <summary>
/// 显示进度
/// </summary>
/// <param name="val"></param>
private void ProgressBar_Value(int val)
{
 progressBar1.Value = val;
 label1.Text = val.ToString() + "%";
}

/// <summary>
/// 下载文件
/// </summary>
/// <param name="url"></param>
/// <param name="savefile"></param>
/// <param name="downloadProgressChanged"></param>
/// <param name="downloadFileCompleted"></param>
private void DownloadFile(string url, string savefile, Action<int> downloadProgressChanged, Action downloadFileCompleted)
{
 WebClient client = new WebClient();
 if (downloadProgressChanged != null)
 {
  client.DownloadProgressChanged += delegate(object sender, DownloadProgressChangedEventArgs e)
  {
   this.Invoke(downloadProgressChanged, e.ProgressPercentage);
  };
 }
 if (downloadFileCompleted != null)
 {
  client.DownloadFileCompleted += delegate(object sender, AsyncCompletedEventArgs e)
  {
   this.Invoke(downloadFileCompleted);
  };
 }
 client.DownloadFileAsync(new Uri(url), savefile);
}
delegate void Action(); //.NET Framework 2.0得自定义委托Action

/// <summary>
/// 点击下载
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button1_Click(object sender, EventArgs e)
{
 DownloadFile("http://xiazai.jb51.net/update.zip", @"F:update.zip", ProgressBar_Value, null);
}