Claims Authentication Helper Class for the Windows Phone 7

The other day I talked about doing Windows Authentication within a Windows Phone 7 application.  I wanted to make it a simpler process so I created a helper class to do this:

public static class ClaimsAuthentication
{
    static WSTrustClient client;

    public static class Endpoints
    {
        public const string AdfsAuthentication = "/adfs/services/trust/13/usernamemixed";
    }

    public static void AuthenticateAsync(string endpoint, 
                                         IRequestCredentials credentials, 
                                         string appliesTo)
    {
        client = GetWSTrustClient(endpoint, credentials);

        var rst = new RequestSecurityToken(WSTrust13Constants.KeyTypes.Bearer)
        {
            AppliesTo = new EndpointAddress(appliesTo)
        };

        client.IssueCompleted += client_IssueCompleted;

        client.IssueAsync(rst);
    }

    private static void client_IssueCompleted(object sender, IssueCompletedEventArgs e)
    {
        client.IssueCompleted -= client_IssueCompleted;

        if (e.Error == null)
            Application.Current.SetPrincipal(e.Result);

        IssueCompleted(sender, e);
    }

    public static event EventHandler<IssueCompletedEventArgs> IssueCompleted;

    private static WSTrustClient GetWSTrustClient(string stsEndpoint, 
                                                  IRequestCredentials credentials)
    {
        return new WSTrustClient(new WSTrustBindingUsernameMixed(), 
                                 new EndpointAddress(stsEndpoint), credentials);
    }
}

You can call it like this:

private void button1_Click(object sender, RoutedEventArgs e)
{
    if (!CheckCredentials())
    {
        MessageBox.Show("Credentials Are Missing.");
        return;
    }

    string endpoint = string.Format("https://{0}{1}", "adfs.example.com", 
                                    ClaimsAuthentication.Endpoints.AdfsAuthentication);

    ClaimsAuthentication.IssueCompleted += new EventHandler
                  <IssueCompletedEventArgs>(ClaimsAuthenticationHelper_IssueCompleted);
    ClaimsAuthentication.AuthenticateAsync(endpoint, 
           new UsernameCredentials(“user”, “pass”), 
           "urn:someapp:blah");
}

void ClaimsAuthenticationHelper_IssueCompleted(object sender, IssueCompletedEventArgs e)
{
    if (e.Error != null)
    {
        showError(e.Error);
        return;
    }

    DoSomething();
}