How to authenticate without prompt to CRM Dynamics Online webservices with ADAL, NetStandard, and Azure AD

I'm currently trying to create a Xamarin App in order to get some info from a Dynamics 365 online instance. The code that authenticate with AD and access the CRM api is deported in a NetStandard (v1.6) Library.

I use the following NuGets :

Microsoft.IdentityModel.Clients.ActiveDirectory (3.13.9)
NETStandard.Library (1.6.1)

I followed the following tutorial in order to link AD with my Dynamics instance : https://nishantrana.me/2016/11/13/register-a-dynamics-365-app-with-azure-active-directory/

Here is my ActiveDirectory helper :

public static class ADHelper
    {

        public async static Task<AuthenticationResult> GetAuthAsync(Uri uri, ClientCredential creditential)
        {
            AuthenticationParameters ap = await AuthenticationParameters.CreateFromResourceUrlAsync(uri);

            String authorityUrl = ap.Authority;
            String resourceUrl = ap.Resource;

            AuthenticationResult result = null;

            AuthenticationContext authContext = new AuthenticationContext(authorityUrl, false);
            result = await authContext.AcquireTokenAsync(resourceUrl, creditential);
            return result;
        }
    }

And my CRM API Client :

public class CRMClient
{
    private AuthenticationResult Auth { get; set; }
    private Uri baseUri { get; set; }

    public CRMClient(Uri uri, ClientCredential creditential)
    {
        baseUri = uri;
        Auth = ADHelper.GetAuthAsync(uri, creditential).Result;
    }

    public void getObject()
    {
        using (HttpClient client = new HttpClient())
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", Auth.AccessToken);
            client.Timeout = new TimeSpan(0, 2, 0);
            client.BaseAddress = baseUri;
            HttpResponseMessage message = client.GetAsync("/accounts").Result;
            String content = message.Content.ReadAsStringAsync().Result;
        }
    }

Parameters used for CRMClient Constructor :