C#下载文件(可显示进度)的方法实现

 在做WIN FORM程序中经常要使用到升级功能，就需要从服务器上下载最新扔软件程序。如何下载呢？代码实现如下：

        /// <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;
             }
         }