Sharing authentication with ASP.NET and Silverlight

I have an ASP.NET web app that includes some silverlight pages. First, the users authenticate using a common ASP.NET webform.

This would be the typical code for that:

FormsAuthentication.SetAuthCookie(this.txtUsername.Text, false);
FormsAuthentication.RedirectFromLoginPage(this.txtUsername.Text, false);
Response.Redirect("~/Private/Index.aspx");

Next, the user navigates to a page that cointains a Silverlight page. From that silverlight page, I need to call some WCF services securely.

The service contains this code:

[ServiceContract(Namespace = "http://mydomain")]
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsM开发者_JS百科ode.Required)]
    public class ServiceWCF
    {
        public ServiceWCF()
        {
            System.ServiceModel.Web.WebOperationContext.Current.OutgoingResponse.StatusCode = System.Net.HttpStatusCode.OK;

            Thread.CurrentPrincipal = HttpContext.Current.User;
        }

        [OperationContract]
        [PrincipalPermission(SecurityAction.Demand, Authenticated = true)]
        public List<Data> GetData()
        {
            // do things
        }
    }

And this is the way I call that method from the silverlight client:

MyWCFReference.ServiceWCFClient proxy = new MyWCFReference.ServiceWCFClient();

proxy.GetDataCompleted += new EventHandler<MyWCFReference.GetDataCompletedEventArgs>(proxy_GetDataCompleted);
proxy.GetDataAsync();

I followed this article to protect my webservices: http://netpl.blogspot.com/2010_04_01_archive.html

But when I run my code, I get the error: Request for principal permission failed.

Any idea about how to solve it? Thaaankkss!!

You probably need to set up a clientaccesspolicy.xml or crossdomain.xml file in the root of the domain where the WCF service is hosted to allow your Silverlight application access.

See this MSDN page for full details.