how to get stream after posting with webClient class

Question

I post to a site using webclient. i use cookiecontainer for holding cookie. I am trying to get stream after posting. and display content to web browser control using stream.

here are my code to get stream, but it gives error. Please guide me where i am wrong.

Error 1 'ExtendedWebClient.GetResponseStream()': no suitable method found to override D:\Project\WorkingCopy\WindowsFormsApplication1\WindowsFormsApplication1\ExtendedWebClient.cs 96 32 WindowsFormsApplication1

public override Stream GetResponseStream()
        {
            var httpWebResponse = _response as HttpWebResponse;
            if (null != httpWebResponse)
            {
                return httpWebResponse.GetCompressedResponseStream();
            }
            else
            {
                return _response.GetResponseStream();
            }
        }