using (WebClient wc = new WebClient())
{
    wc.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
    string HtmlResult = wc.UploadString(url, "sign=fsadfasdf&charset=utf-8");
}
Server can get value of sign and charset.
But there is a third parameter LIST, which is a list of object (this object is an entity class). How can I pass this parameter to the server?
I tried to use "sign=fsadfasdf&charset=hhh&list=" + Json(list) as postData (convert List to json string).  But the server didn't get value of this list param.
 
     
    