var url = "address";
var cookieContainer = new CookieContainer();
using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
using (var client = new HttpClient(handler) { })
{
cookieContainer.Add(new Uri("youdomain"), new Cookie("cookieName", "cookieValue"));
var result = client.GetStringAsync(url).Result;
return Content(result);
}