Http post wth WebClient

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C#

HTTP

Hello everyone:
I am new in .net programming and need some help. My intention is to post data to a web server and get desired service. The functionality of the program in my mind is that:
After an initial log-in session with username/password, the following sessions only accepts key-value pairs for a required service -- this is the way the server supposed to provide the service.

I found an implementation code for a Cookie-awared WebClient class that may be a solution, attached as following. But it does not work. The problem is: the cookies from the first session was not well captured, so subsequent sessions lack the desired information to work properly.

Is there a more detailed example on how to realize the function?

Thank you in advance!

Jacob

public class WebClient_CookieAware : WebClient
 {
     public CookieContainer theCookieContainer { get; set; }
     public Uri Uri { get; set; }
     public WebClient_Cookie(): this(new CookieContainer())
          {    }

     public WebClient_Cookie(CookieContainer cookies)
        {
         this.theCookieContainer = cookies;
         }

     protected override WebRequest GetWebRequest(Uri address)
     {
         WebRequest request = base.GetWebRequest(address);
         if (request is HttpWebRequest)
             { (request as HttpWebRequest).CookieContainer = theCookieContainer;}
         HttpWebRequest httpRequest = (HttpWebRequest)request;
         // httpRequest.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
         return httpRequest;
     }

     protected override WebResponse GetWebResponse(WebRequest request)
     {
         WebResponse response = base.GetWebResponse(request);
         String setCookieHeader = response.Headers[HttpResponseHeader.SetCookie];
         if (setCookieHeader == null)
         {
             Cookie cookie = new Cookie();
             this.theCookieContainer.Add(cookie);
         }
         return response;
     }
 }