Windows Phone 8.1. http get request self signed certificate

I would like to connect to a url and authenticate me with a certificate. I've added my certificate to the assets.

I have the following code in the OnLaunched method in App.xaml.cs:

try
        {
            System.Uri certificateFile = new System.Uri("ms-appx:///Assets/filenme.crt");

            Windows.Storage.StorageFile file = await Windows.Storage.StorageFile.GetFileFromApplicationUriAsync(certificateFile);
            Windows.Storage.Streams.IBuffer certBlob = await Windows.Storage.FileIO.ReadBufferAsync(file);

            Windows.Security.Cryptography.Certificates.Certificate rootCert = new Windows.Security.Cryptography.Certificates.Certificate(certBlob);
            rootCert.FriendlyName = "Root";
            Windows.Security.Cryptography.Certificates.CertificateStore trustedStore = Windows.Security.Cryptography.Certificates.CertificateStores.TrustedRootCertificationAuthorities;
            trustedStore.Add(rootCert);
            System.Diagnostics.Debug.WriteLine(rootCert.FriendlyName);
            System.Diagnostics.Debug.WriteLine(trustedStore);
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine("Certificate: " + ex.Message);
        }

And the following code at my request:

            CertificateQuery certQuery = new CertificateQuery();
            certQuery.FriendlyName = "Root";
            IReadOnlyList<Certificate> certs = await CertificateStores.FindAllAsync(certQuery);

            System.Diagnostics.Debug.WriteLine(certs.Count);

            HttpBaseProtocolFilter protolFilter = new HttpBaseProtocolFilter();

            protolFilter.ClientCertificate = certs[0];
            HttpClient client = new HttpClient(protolFilter);
            var response = await client.GetAsync(url);

            Certificate aCertificate = response.RequestMessage.TransportInformation.ServerCertificate;
            IBuffer certBlob = aCertificate.GetCertificateBlob();


            response.EnsureSuccessStatusCode();

            string content = await response.Content.ReadAsStringAsync();
            return content;

The problem is that I get the error that my certificate is OutOfRange at this line:

protolFilter.ClientCertificate = certs[0];

Why is my certificate not in the list of ClientCertificates? Please help me. Thanks