source: extensions/PiwigoLib/PiwigoLib/Proxy/PwgGenericProxy.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.IO;

using System.Web;
using System.Xml.Serialization;
using System.Xml;
using System.Collections.Specialized;

namespace Com.Piwigo.Lib.Proxy
{

    static internal class PwgGenericProxy<T>
    {
        /// <summary>
        /// Send Get data request to piwigo
        /// </summary>
        /// <param name="address"></param>
        /// <param name="methodName"></param>
        /// <param name="methodParameter"></param>
        /// <returns></returns>
        internal static T Get(Uri address, String methodName, String methodParameter)
        {
            T ReturnValue = default(T);
            HttpWebRequest Request;
            HttpWebResponse Response = null;
            StreamReader Reader;

            if (address == null) { throw new PwgProxyException("The get address is null."); }

            try
            {
                UriBuilder completeUri = new UriBuilder(address);
                if (methodParameter == null)
                {
                    completeUri.Query = String.Format("method={0}", methodName);
                }
                else
                {
                    completeUri.Query = String.Format("method={0}&{1}", methodName, methodParameter);
                }
                // Create and initialize the web request  
                Request = WebRequest.Create(completeUri.Uri) as HttpWebRequest;
                Request.UserAgent = PwgConfigProxy.PwgUserAgent;
                Request.KeepAlive = PwgConfigProxy.PwgKeepAlive;
#if DEBUG
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000 * 1000;
#else
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000;
#endif

                Request.CookieContainer = PwgConfigProxy.cookieContainer; // get session cookie

                // Get response  
                Response = Request.GetResponse() as HttpWebResponse;

                if (Request.HaveResponse == true && Response != null)
                {
                    // Get the response stream  
                    Reader = new StreamReader(Response.GetResponseStream());

                    ReturnValue = DeserializeObject(Reader);
                }
            }
            catch (WebException wex)
            {
                // This exception will be raised if the server didn't return 200 - OK  
                // Try to retrieve more information about the network error  
                if (wex.Response != null)
                {
                    using (HttpWebResponse errorResponse = (HttpWebResponse)wex.Response)
                    {
                        throw new PwgProxyException(
                            String.Format(
                                "The server returned '{0}' with the status code {1} ({2:d}).",
                                errorResponse.StatusDescription, errorResponse.StatusCode,
                                errorResponse.StatusCode),
                                wex);
                    }
                }
            }
            finally
            {
                if (Response != null) { Response.Close(); }
            }
            return ReturnValue;
        }

        /// <summary>
        /// Send Post data request to piwigo
        /// </summary>
        /// <param name="address"></param>
        /// <param name="data"></param>
        /// <returns></returns>
        internal static T Post(Uri address, String data)
        {
            T ReturnValue = default(T);
            //System.Net.ServicePointManager.Expect100Continue = false;

            HttpWebRequest Request;
            HttpWebResponse Response = null;

            if (address == null) { throw new PwgProxyException("The get address is null."); }

            try
            {
                // Create the web request  
                Request = WebRequest.Create(address) as HttpWebRequest;
                Request.UserAgent = PwgConfigProxy.PwgUserAgent;
                Request.KeepAlive = PwgConfigProxy.PwgKeepAlive;
#if DEBUG
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000 * 1000;
#else
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000;
#endif

                Request.CookieContainer = PwgConfigProxy.cookieContainer; // get session cookie

                // Set type to POST  
                Request.Method = "POST";
                Request.ContentType = "application/x-www-form-urlencoded";

                // Create a byte array of the data we want to send  
                byte[] byteData = UTF8Encoding.UTF8.GetBytes(data);

                // Set the content length in the request headers  
                Request.ContentLength = byteData.Length;

                // Write data  
                using (Stream PostStream = Request.GetRequestStream())
                {
                    PostStream.Write(byteData, 0, byteData.Length);
                }

                // Get response  
                using (Response = Request.GetResponse() as HttpWebResponse)
                {
                    // Get the response stream  
                    StreamReader reader = new StreamReader(Response.GetResponseStream());

                    ReturnValue = DeserializeObject(reader);
                }
            }
            catch (WebException wex)
            {
                // This exception will be raised if the server didn't return 200 - OK  
                // Try to retrieve more information about the network error  
                if (wex.Response != null)
                {
                    using (HttpWebResponse ErrorResponse = (HttpWebResponse)wex.Response)
                    {
                        throw new PwgProxyException(
                            String.Format(
                                "The server returned '{0}' with the status code {1} ({2:d}).",
                                ErrorResponse.StatusDescription, ErrorResponse.StatusCode,
                                ErrorResponse.StatusCode),
                            wex);
                    }
                }
            }
            finally
            {
                if (Response != null) { Response.Close(); }
            }
            return ReturnValue;
        }

        private class MimePart
        {
            internal NameValueCollection Headers { get; set; }
            internal byte[] Header { get; set; }
            internal Stream Data { get; set; }

            internal MimePart()
            {
                Headers = new NameValueCollection();
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="address">URI of server</param>
        /// <param name="dcFiles">Dictionary(String NameOfFileFiel, String FilePath) FilePath must exist on hdd</param>
        /// <param name="dcFields">Dictionary(String NameOfFormField, String ValueForField) others form filed to submit</param>
        /// <returns></returns>
        internal static T PostAsMultiPartForm(Uri address, Dictionary<String, String> dcFiles, Dictionary<String, String> dcFields)
        {            
            List<MimePart> lstMimeParts = new List<MimePart>();
            T ReturnValue = default(T);

            HttpWebRequest Request;
            HttpWebResponse Response = null;
            
            if (address == null) { throw new PwgProxyException("The get address is null."); }

            try
            {
                // Create the web request  
                Request = WebRequest.Create(address) as HttpWebRequest;
                Request.UserAgent = PwgConfigProxy.PwgUserAgent;
                Request.KeepAlive = PwgConfigProxy.PwgKeepAlive;
#if DEBUG
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000 * 1000;
#else
                Request.Timeout = PwgConfigProxy.PwgTimeOutInSecond * 1000;
#endif
                Request.SendChunked = true;
                Request.ProtocolVersion = System.Net.HttpVersion.Version11;
                Request.CookieContainer = PwgConfigProxy.cookieContainer; // get session cookie        

                // MultiPart Post Request
                Request.ContentType = "multipart/form-data;";
                Request.Method = "POST";

                // Loading Mine Part data from others form fields
                foreach (string key in dcFields.Keys)
                {
                    MimePart part = new MimePart();
                    part.Headers["Content-Disposition"] = "form-data; name=\"" + key + "\"";
                    part.Data = new MemoryStream(Encoding.UTF8.GetBytes(dcFields[key]));
                    lstMimeParts.Add(part);
                }

                // Loading MinePart data from form file fields
                foreach (String strFieldName in dcFiles.Keys)
                {
                    MimePart part = new MimePart();
                    part.Headers["Content-Disposition"] = "form-data; name=\"" + strFieldName + "\"; filename=\"" + dcFiles[strFieldName] + "\"";
                    part.Headers["Content-Type"] = "application/octet-stream";
                    part.Data = File.OpenRead(dcFiles[strFieldName]); // Open file for getting a stream reader on it.
                    lstMimeParts.Add(part);
                }

                string strBound = "----------" + DateTime.Now.Ticks.ToString("x");
                byte[] strFooter = Encoding.UTF8.GetBytes("--" + strBound + "--\r\n");
                Request.ContentType += " boundary=" + strBound;

                long contentLength = 0;
                foreach (MimePart part in lstMimeParts)
                {                   
                    StringBuilder sb = new StringBuilder();

                    sb.Append("--");
                    sb.Append(strBound);
                    sb.AppendLine();
                    foreach (string key in part.Headers.AllKeys)
                    {
                        sb.Append(key);
                        sb.Append(": ");
                        sb.AppendLine(part.Headers[key]);
                    }
                    sb.AppendLine();

                    part.Header = Encoding.UTF8.GetBytes(sb.ToString());

                    contentLength += part.Header.Length + part.Data.Length + 2;

                }

                Request.ContentLength = contentLength + strFooter.Length;

                byte[] buffer = new byte[8192];
                byte[] afterFile = Encoding.UTF8.GetBytes("\r\n");
                int read;

                using (Stream s = Request.GetRequestStream())
                {
                    foreach (MimePart part in lstMimeParts)
                    {
                        s.Write(part.Header, 0, part.Header.Length);

                        while ((read = part.Data.Read(buffer, 0, buffer.Length)) > 0)
                            s.Write(buffer, 0, read);

                        part.Data.Close();
                        part.Data.Dispose();

                        s.Write(afterFile, 0, afterFile.Length);
                    }

                    s.Write(strFooter, 0, strFooter.Length);
                }

                // Get response  
                using (Response = Request.GetResponse() as HttpWebResponse)
                {
                    // Get the response stream  
                    StreamReader reader = new StreamReader(Response.GetResponseStream());

                    ReturnValue = DeserializeObject(reader);
                }
            }
            catch (WebException wex)
            {
                // This exception will be raised if the server didn't return 200 - OK  
                // Try to retrieve more information about the network error  
                if (wex.Response != null)
                {
                    using (HttpWebResponse ErrorResponse = (HttpWebResponse)wex.Response)
                    {
                        throw new PwgProxyException(
                            String.Format(
                                "The server returned '{0}' with the status code {1} ({2:d}).",
                                ErrorResponse.StatusDescription, ErrorResponse.StatusCode,
                                ErrorResponse.StatusCode),
                            wex);
                    }
                }
            }
            catch (IOException ioex)
            {
                // This exception will be raised if file aren't ok on client
                if (ioex!= null)
                {
                        throw new PwgProxyException(
                            String.Format(
                                "A IO file exception stop the request building : {0}.", ioex.Message),
                            ioex);
                }
            }
            finally
            {
                if (Response != null) { Response.Close(); }
                foreach (MimePart part in lstMimeParts)
                {
                    if (part.Data != null)
                        part.Data.Dispose();
                }
            }
            return ReturnValue;
        }
    
        /// <summary>
        ///  return object from xml retuned by piwigo
        /// </summary>
        /// <param name="xmlData"></param>
        /// <returns></returns>
        internal static T DeserializeObject(StreamReader xmlData)
        {
            T ReturnValue = default(T);
            String line = String.Empty;
            try
            {
#if DEBUG
                line = xmlData.ReadToEnd();
                System.Diagnostics.Debug.WriteLine(line);

                byte[] hexLine = System.Text.Encoding.UTF8.GetBytes(line);
                MemoryStream m = new System.IO.MemoryStream(hexLine);
                StreamReader xmlDat = new StreamReader(m);
#else
                xmlDat = xmlData;
#endif
                System.Xml.Serialization.XmlSerializer xsSerializer = new System.Xml.Serialization.XmlSerializer(typeof(T));
                ReturnValue = (T)xsSerializer.Deserialize(xmlDat);
            }
            catch (Exception ex)
            {
                throw new PwgProxyException(
                            String.Format(
                                "The value {0} can't be deserialized in {1}, the error is {2} .",
                                line, typeof(T).Name, ex.Message),
                            ex);
            }

            return ReturnValue;
        }

        internal static void SerializeToXML(String fileName, T obj)
        {
            try
            {
                XmlSerializer serializer = new XmlSerializer(typeof(T));
                TextWriter textWriter = new StreamWriter(fileName);
                serializer.Serialize(textWriter, obj);
                textWriter.Close();
            }
            catch (Exception ex)
            {
                throw new PwgProxyException(
                            String.Format(
                                "The value {0} can't be serialized in {1}, the error is {2} .",
                                obj, fileName, ex.Message),
                            ex);
            }
        }
    }
}