上载进度条的实现

<ProgressBar Name="Prog" Margin="29,72,23,0" Height="27" VerticalAlignment="Top">            
        </ProgressBar>

/// <summary>
        /// 下载文件
        /// </summary>
        /// <param name="filename"></param>
        private void DownLoadFile(string URL, string Filename, ProgressBar pm)
        {
            //WebClient wc = new WebClient();
            try
            {
                //Uri address = new Uri(URL + Filename);
                //wc.DownloadFile(address, Filename);
                //从URL地址得到一个WEB请求
                System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL + Filename);
                //从WEB请求得到WEB响应 
                System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)Myrq.GetResponse();
                //从WEB响应得到总字节数
                long totalBytes = myrp.ContentLength;
                //从总字节数得到进度条的最大值
                pm.Maximum = (int)totalBytes;
                //从WEB请求创建流（读）
                System.IO.Stream st = myrp.GetResponseStream();
                //确定下载文件的路径
                string DownLoadPath = @"C:\SalesReport\" + Filename;
                //创建文件流（写）
                System.IO.Stream so = new System.IO.FileStream(DownLoadPath, System.IO.FileMode.Create);
                //下载文件大小
                long totalDownloadedByte = 0;
                byte[] by = new byte[1024];
                //读流
                int osize = st.Read(by, 0, (int)by.Length);
                while (osize > 0)
                {
                    //更新文件大小
                    totalDownloadedByte = osize + totalDownloadedByte;
                    //写流 
                    so.Write(by, 0, osize);
                    //更新进度条 
                    pm.Value = (int)totalDownloadedByte;
                    //读流
                    osize = st.Read(by, 0, (int)by.Length);
                }
                //关闭流
                so.Close();
                //关闭流
                st.Close();
            }
            catch (Exception ex)
            {
                throw new Exception("下载更新文件出错：" + ex.Message);
            }
        }