带有用户名密码验证的远程文件下载

 try
            {
                string getFileName = Url.Substring(Url.LastIndexOf("/") + 1);

                HttpWebRequest WRequest;
               // HttpWebResponse response = null;
                Uri uri = new Uri(Url);
                CredentialCache cc = new CredentialCache();
                WRequest = (HttpWebRequest)HttpWebRequest.Create(uri);
                WRequest.Credentials = new System.Net.NetworkCredential(DocLibConst.Con_SPUserName, DocLibConst.Con_PWD, DocLibConst.Con_Domain);
                WRequest.PreAuthenticate = true;
                WRequest.Method = "GET";
                WRequest.AllowWriteStreamBuffering = false;
                WRequest.SendChunked = false;
                WRequest.KeepAlive = true;
                WRequest.ContentLength = 0;

                //WRequest.SendChunked = true;
                //WRequest.ContentLength = 100000;
                WRequest.Timeout = 30000;
                WRequest.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(new ASCIIEncoding().GetBytes("epapi:epapiadmin")));
                WebResponse wr = WRequest.GetResponse();
                Stream responseStream = wr.GetResponseStream();
                MemoryStream mem = new MemoryStream();
                //创建本地文件写入流
                //Stream stream = new FileStream("D:\\xx.docx", FileMode.Create);

                byte[] bArr = new byte[1024];
                int size = responseStream.Read(bArr, 0, (int)bArr.Length);
                while (size > 0)
                {
                    //stream.Write(bArr, 0, size);
                    mem.Write(bArr, 0, size);
                    size = responseStream.Read(bArr, 0, (int)bArr.Length);
                }
                //stream.Write(mem.ToArray(), 0, mem.ToArray().Length);
                //stream.Close();
                responseStream.Close();


                Page.Response.ClearContent();
                Page.Response.ClearHeaders();
                Page.Response.AddHeader("Content-Disposition", "attachment; filename="
                    + HttpUtility.UrlEncode(getFileName, System.Text.Encoding.UTF8));

                Page.Response.AddHeader("Content-Length", mem.ToArray().Length.ToString());
                Page.Response.AddHeader("Content-Transfer-Encoding", "binary");
                Page.Response.ContentType = "application/octet-stream";

                Page.Response.BinaryWrite(mem.ToArray());
                Page.Response.Flush();
                //page.Response.End();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                HttpContext.Current.Response.Close();
            }