如何在ASP.NET中利用WebClient上传图片到远程服务？

<form id="Form1" method="post" runat="server" enctype="multipart/form-data">
<input id="MyFile" type="file" runat="server" />
<br />
<br />
<asp:Button ID="Button1" runat="server" Text="上载文件" OnClick="Button1_Click"></asp:Button>
</form>

System.Web.HttpFileCollection oFiles = System.Web.HttpContext.Current.Request.Files;
  string FilePath = oFiles[0].FileName;
  string FileName = FilePath.Substring(FilePath.LastIndexOf("\\") + 1);
  byte[] b = new byte[oFiles[0].ContentLength];
  System.IO.Stream fs = (System.IO.Stream)oFiles[0].InputStream;
  fs.Read(b, 0, oFiles[0].ContentLength);
  string postData = "data=" + HttpUtility.UrlEncode(Convert.ToBase64String(b));
  var webclient = new WebClient();
  webclient.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
  byte[] byteArray = Encoding.UTF8.GetBytes(postData);
  //byte[] buffer = webclient.UploadData("http://localhost/datapush/DataPush.ashx", "POST", byteArray);//ashx
  byte[] buffer = webclient.UploadData("http://localhost/datapush/WebServiceDataPush.asmx/DataPush", "POST", byteArray);//asmx
  var msg = Encoding.UTF8.GetString(buffer);
  Response.Write(msg);

string msg = "";
  byte[] filedata = Convert.FromBase64String(context.Request["data"]);
  if (filedata.Length == 0)
  {
  msg= "{\"code\":\"上传的是空文件\"}";
  }
  if (filedata.Length > 1048576)
  {
  msg = "{\"code\":\"图片大小不能超过1M\"}";
  }
  string fileextension = filedata[0].ToString() + filedata[1].ToString();
  if (fileextension == "7173")
  {
  fileextension = "gif";
  }
  else if (fileextension == "255216")
  {
  fileextension = "jpg";
  }
  else if (fileextension == "13780")
  {
  fileextension = "png";
  }
  else if (fileextension == "6677")
  {
  fileextension = "bmp";
  }
  else if (fileextension == "7373")
  {
  fileextension = "tif";
  }
  else
  {
  msg = "{\"code\":\"上传的文件不是图片\"}";
  }
  try
  {
  //保存图片
  string filename = Guid.NewGuid().ToString("D") + "." + fileextension;
  System.IO.MemoryStream ms = new System.IO.MemoryStream(filedata);
  System.IO.FileStream fs = new System.IO.FileStream(context.Server.MapPath("~/") + "/采集图片/" + filename, System.IO.FileMode.Create);
  ms.WriteTo(fs);
  ms.Close();
  fs.Close();
  fs = null;
  ms = null;
  msg = "{\"code\":\"上传图片成功\"}";
  }
  catch (Exception exe)
  {
  msg = "{\"code\":\"" + exe.Message + "\"}";
  }