Sending base64 string using HttpWebRequest in C # convert "+" to space issue

i convert image to base64 string for upload via HttpWebRequest in c # .on server side, when i get base64 string, "+" signs were converted to white spaces ". it gives me error to convert this base64 string to byte array. i do not want to make any changes on the server side (in web services) I want to solve these problems on the client side The client code of the client is as follows.

//////////////////

WSManagerResult wsResult = new WSManagerResult ();

        try
        {
            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(serviceURL);
            req.Method = "POST";
            req.ProtocolVersion = HttpVersion.Version11;
            req.ContentType = "application/x-www-form-urlencoded";
            //  req.ContentType = "application/x-www-form-urlencoded; charset=utf-8";
            // req.CookieContainer = new CookieContainer();


            string content = string.Empty;
            foreach (KeyValuePair<string, string> entry in paramDic)
            {

      

        
        
        
      

    

//entry.Value is the base 64-line gene evaluated from the image

             content = content + entry.Key + "=" + entry.Value + "&&";
            }
            content = content.TrimEnd('&'); // input parameter if u have more that one //a=b&dd=aa               
            req.ContentLength = content.Length;
            // req = URLEncode(content);
            Stream wri = req.GetRequestStream();


            byte[] array = Encoding.ASCII.GetBytes(content);
            if (array.Length > 0)
                wri.Write(array, 0, array.Length);
            wri.Flush();
            wri.Close();
            WebResponse rsp = (HttpWebResponse)req.GetResponse();


            byte[] b = null;
            using (Stream stream = rsp.GetResponseStream())
            using (MemoryStream ms = new MemoryStream())
            {
                int count = 0;
                do
                {
                    byte[] buf = new byte[1024];
                    count = stream.Read(buf, 0, 1024);
                    ms.Write(buf, 0, count);
                } while (stream.CanRead && count > 0);
                b = ms.ToArray();
            }
            wsResult.result = Encoding.ASCII.GetString(b);
        }
        catch (Exception e)
        {
            clsException.ExceptionInstance.HandleException(e);
            wsResult.error = e.Message;
        }


        return wsResult;

      

        
        
        
      

    

All "+" signs in the base64 string are converted to "white spaces". This causes the problem described above.

Please help me to solve this problem.

Hello

Shah Khalid