Struggling trying to get cookie out of response with HttpClient in .net 4.5

To add cookies to a request, populate the cookie container before the request with CookieContainer.Add(uri, cookie). After the request is made the cookie container will automatically be populated with all the cookies from the response. You can then call GetCookies() to retreive them.

CookieContainer cookies = new CookieContainer();
HttpClientHandler handler = new HttpClientHandler();
handler.CookieContainer = cookies;

HttpClient client = new HttpClient(handler);
HttpResponseMessage response = client.GetAsync("http://google.com").Result;

Uri uri = new Uri("http://google.com");
IEnumerable<Cookie> responseCookies = cookies.GetCookies(uri).Cast<Cookie>();
foreach (Cookie cookie in responseCookies)
    Console.WriteLine(cookie.Name + ": " + cookie.Value);

Console.ReadLine();

Not in every case you can add httpClientHandler to httpClient. For example, when you use integration tests testServer.CreateClient() or inject httpClient from IHttpClientFactory. So, I have simply read values from header.

    public static List<Cookie> GetCookies(this HttpResponseMessage message)
    {
        message.Headers.TryGetValues("Set-Cookie", out var cookiesHeader);
        var cookies = cookiesHeader.Select(cookieString => CreateCookie(cookieString)).ToList();
        return cookies;
    }

    private static Cookie CreateCookie(string cookieString)
    {
        var properties = cookieString.Split(';', StringSplitOptions.TrimEntries);
        var name = properties[0].Split("=")[0];
        var value = properties[0].Split("=")[1];
        var path = properties[2].Replace("path=", "");
        var cookie = new Cookie(name, value, path)
        {
            Secure = properties.Contains("secure"),
            HttpOnly = properties.Contains("httponly"),
            Expires = DateTime.Parse(properties[1].Replace("expires=", ""))
        };
        return cookie;
    }

CreateCookie method may be modified to exactly match your cookie properties.

You can easily get a cookie value with the given URL.

private async Task<string> GetCookieValue(string url, string cookieName)
{
    var cookieContainer = new CookieContainer();
    var uri = new Uri(url);
    using (var httpClientHandler = new HttpClientHandler
    {
        CookieContainer = cookieContainer
    })
    {
        using (var httpClient = new HttpClient(httpClientHandler))
        {
            await httpClient.GetAsync(uri);
            var cookie = cookieContainer.GetCookies(uri).Cast<Cookie>().FirstOrDefault(x => x.Name == cookieName);
            return cookie?.Value;
        }
    }
}

There's alternative if you don't have access to the HttpClient and can't inject the CookieContainer. This works in .NET Core 2.2:

private string GetCookie(HttpResponseMessage message)
{
    message.Headers.TryGetValues("Set-Cookie", out var setCookie);
    var setCookieString = setCookie.Single();
    var cookieTokens = setCookieString.Split(';');
    var firstCookie = cookieTokens.FirstOrDefault();
    var keyValueTokens = firstCookie.Split('=');
    var valueString = keyValueTokens[1];
    var cookieValue = HttpUtility.UrlDecode(valueString);
    return cookieValue;
}