首頁要在窗體上拖progressBar、label和button三個控件，拖到適當的位置

雙擊button按紐，在里面加上代碼
private void button1_Click(object sender, EventArgs e)
{
   //點擊開始下載
   string url = "http://www.aspbc.com/1.rar";//這里換成你要下載的文件
   DownloadFile(url, @"F:\" + System.IO.Path.GetFileName(url), progressBar1, label1);
}

/// <summary>        

/// c#.net 下載文件

/// </summary>

/// <param name="URL">下載文件地址</param>

/// <param name="Filename">下載后的存放地址</param>

/// <param name="Prog">用于顯示的進度條</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;

           string s2 = String.Format("{0:N2}", percent);

           label1.Text = "正在下載，下載進度" + s2 + "%";

           System.Windows.Forms.Application.DoEvents(); //必須加注這句代碼，否則label1將因為循環執行太快而來不及顯示信息

        }                

        so.Close();

        st.Close();

        //下載完成

        label1.Text = "下載完成";                

    }

    catch (System.Exception)

    {

        throw;

     }

}