Csharp:WebClient and WebRequest use http download file

//Csharp:WebClient and WebRequest use http download file            //20140318 塗聚文收錄            string filePath = "20140302.pdf";            string fileName = "http://www.dusystem.com/3.pdf";            //1出现找不到文件 filePath            //string headerValue = (Request.UserAgent.ToLower().Contains("msie"))? string.Format("attachment; filename=/"{0}/"", Uri.EscapeDataString(fileName)): string.Format("attachment; filename=/"{0}/"", fileName); //for Firefox, Chrome, Safari, Opera            //Response.Clear();            //Response.ContentType = "text/plain";            //Response.AddHeader("Content-Disposition", headerValue);            //Response.TransmitFile(filePath);            //Response.End();            //2： 有效   WebException ex            //System.Net.WebClient net = new System.Net.WebClient();            //string link = fileName;            //Response.ClearHeaders();            //Response.Clear();            //Response.Expires = 0;            //Response.Buffer = true;            //Response.AddHeader("Accept-Language", "utf-8");            //Response.AddHeader("Content-Disposition", "Attachment;FileName=" + System.Web.HttpUtility.UrlEncode(link, System.Text.Encoding.UTF8));            //Response.ContentType = "application/octet-stream";            //Response.BinaryWrite(net.DownloadData(link));            //Response.End();            //3:有效,但文件是空            //string dir = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);            //string myFileName = dir + @"/213.pdf";            //HttpWebRequest request = (HttpWebRequest)WebRequest.Create(fileName);  //                      //request.MaximumResponseHeadersLength = 40000;            //request.Timeout = 20000;            //request.Credentials = CredentialCache.DefaultCredentials;            //HttpWebResponse response = (HttpWebResponse)request.GetResponse();            //Stream receiveStream = response.GetResponseStream();            //StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8);            //using (StreamWriter sw = new StreamWriter(myFileName, false, Encoding.UTF8))            //{            //    sw.Write(readStream.ReadToEnd());            //    sw.Flush();            //    sw.Close();            //}            //4。有效            //byte[] result;            //byte[] buffer = new byte[4096];            //string link = fileName;            //WebRequest wr = WebRequest.Create(fileName);            //WebResponse response = wr.GetResponse();            //Stream responseStream = response.GetResponseStream();            //MemoryStream memoryStream = new MemoryStream();            //Response.AddHeader("Accept-Language", "utf-8");            //Response.AddHeader("Content-Disposition", "Attachment;FileName=" + System.Web.HttpUtility.UrlEncode(link, System.Text.Encoding.UTF8));            //Response.ContentType = "APPLICATION/octet-stream";            //int count = 0;            //do            //{            //    count = responseStream.Read(buffer, 0, buffer.Length);            //    memoryStream.Write(buffer, 0, count);            //    Response.BinaryWrite(buffer);            //    //Response.OutputStream.Write(buffer,0,count);            //}            //while (count != 0);            //result = memoryStream.ToArray();            //5。有效            string dir = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);            string fullFileName = dir + @"/213.pdf";            HttpWebRequest hRequest = (HttpWebRequest)WebRequest.Create(fileName);            WebResponse response = hRequest.GetResponse();            using (response = (HttpWebResponse)hRequest.GetResponse())            {                /*Download the file to the fullFileName location */                Stream streamResponse = response.GetResponseStream();                if (streamResponse != null)                {                    byte[] inBuf = new byte[response.ContentLength];                    int bytesToRead = System.Convert.ToInt32(inBuf.Length);                    int bytesRead = 0;                    while (bytesToRead > 0)                    {                        int n = streamResponse.Read(inBuf, bytesRead, bytesToRead);                        if (n == 0)                        {                            break;                        }                        bytesRead += n;                        bytesToRead -= n;                    }                    FileStream fstr = new FileStream(fullFileName, FileMode.OpenOrCreate, Fileaccess.Write);                    fstr.Write(inBuf, 0, bytesRead);                    streamResponse.Close();                    streamResponse.Dispose();                    fstr.Close();                    fstr.Dispose();                }            }