Access WebAPI with AntiForgeryToken in Aspnet 5.0 on Xamarin

i'm trying to access a WebAPI which is using ValidateAntiForgeryToken. My WebAPI Method is this (a simple one), which is inside a User Controller (just for a test):

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Test(String field)
{
    String result = String.Empty;
    if (ModelState.IsValid)
    {
        HtmlSanitizer sanitizer = new HtmlSanitizer();

        try
        {
            result = sanitizer.Sanitize(field);
        }
        catch (Exception ex)
        {
            result = ex.Message;
            throw;
         }
    }
    return Json(result);
}

With Ajax, i can access it with ease:

$.ajax({
    url: '/User/Test',
     type: "POST",
    contentType: "application/x-www-form-urlencoded",

    data: {

        field: self.textField(),
         __RequestVerificationToken: $("input[name='__RequestVerificationToken']").val(),
    },
    success: function(e) {
       self.textField(e)
        self.divField(e);
    },
    error: function(e) {
        console.log(e.error());
    },
});

But, until now, i can't access this webapi with httpclient on xamarin. This is my code:

    private async void DoTestWebApi()
{
    try
    {
        HttpClient clientPage = new HttpClient()
        {
            BaseAddress = new Uri("https://localhost:44356/user")
        };

        var pageWithToken = await clientPage.GetAsync(clientPage.BaseAddress);

        String verificationToken = GetVerificationToken(await pageWithToken.Content.ReadAsStringAsync());

        HttpClient client = new HttpClient()
        {
            BaseAddress = new Uri("https://localhost:44356/user/test/")
        };

        HttpRequestMessage message = new HttpRequestMessage()
        {
            RequestUri = new Uri("https://localhost:44356/user/test/"),
            Method = HttpMethod.Post
        };

        message.Headers.Add("__RequestVerificationToken", verificationToken);

        String field = "teste";

        //StringContent content = new StringContent("field=test", Encoding.UTF8, "application/x-www-form-urlencoded");
        StringContent content = new StringContent("__RequestVerificationToken=" + verificationToken + ",field=test", Encoding.UTF8, "application/x-www-form-urlencoded");

        // this doesn't work
        //client.DefaultRequestHeaders.Add("__RequestVerificationToken", verificationToken);
        var response2 = await client.SendAsync(message);

        if (response2.IsSuccessStatusCode)
        {
            var t = response2.Content.ReadAsStringAsync();

            if (true)
            {
                // just to check if t has value
            }
        }

    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
        throw;
    }

}

Honestly, i don't know what else i could do to pass my anti forgery token inside the message. It works perfectly in ajax, i pass it inside the data content, but in xamarin it doesn't work. All the code is executed inside the same localhost. If i remove the [ValidateAntiForgeryToken], it works.

What am i missing?

Edit:

Ok, so now i'm sending with cookies, but is not hitting the method again. This is my update:

HttpClient clientPage = new HttpClient()
{
    BaseAddress = new Uri("https://localhost:44356/user")
};

var pageWithToken = await clientPage.GetAsync(clientPage.BaseAddress);

String verificationToken = GetVerificationToken(await pageWithToken.Content.ReadAsStringAsync());

List<KeyValuePair<String, String>> cookiesInfo = new List<KeyValuePair<String, String>>();

foreach (var item in pageWithToken.Headers)
{
    cookiesInfo.Add(new KeyValuePair<String, String>(item.Key, item.Value.ToString()));
}

cookiesInfo.Add(new KeyValuePair<string, string>("field", "value"));
cookiesInfo.Add(new KeyValuePair<string, string>("__RequestVerificationToken", verificationToken));

CookieContainer cookieContainer = new CookieContainer();

using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
{
    using (var client = new HttpClient(handler) { BaseAddress = new Uri("https://localhost:44356/user") })
    {
        var content = new FormUrlEncodedContent(cookiesInfo);

        cookieContainer.Add(client.BaseAddress, new Cookie("__RequestVerificationToken", verificationToken));

        foreach (var item in cookiesInfo)
        {
            cookieContainer.Add(client.BaseAddress, new Cookie(item.Key, item.Value));
        }

        var result = client.PostAsync(new Uri("https://localhost:44356/user/test"), content).Result;

        result.EnsureSuccessStatusCode();
    }

};

This is driving me nuts... Ok the test is in localhost but soon this app will be in Azure, and this is a pre-requisite...

Edit: GetVerificationToken Method:

private string GetVerificationToken(String verificationToken)
    {
        if (verificationToken != null && verificationToken.Length > 0)
        {
            verificationToken = verificationToken.Substring(verificationToken.IndexOf("__RequestVerificationToken"));
            verificationToken = verificationToken.Substring(verificationToken.IndexOf("value=\"") + 7);
            verificationToken = verificationToken.Substring(0, verificationToken.IndexOf("\""));
        }

        return verificationToken;
    }