Windows authentication in Silverlight

Authenticating a windows user from a Silverlight application is pretty simple with the following steps

1.Create a WCF service with a method to Authenticate the windows user

Interface

[ServiceContract]
    public interface IUser
    {
        [OperationContract]
        bool AuthenticateUser(string UserName, string Password);
    }

Class

public class User : IUser
   {
       public bool AuthenticateUser(string UserName, string Password)
       {
           return (Helper.LogOnUser(UserName.Split(new string[] { "@" }, StringSplitOptions.RemoveEmptyEntries)[0],
                       "microsoft.com",
                       Password
                       ) != 0);
       }

   }

Helper class

public static class Helper
       {
           #region Properties
           private const int LOGON32_LOGON_INTERACTIVE = 2;
           private const int LOGON32_PROVIDER_DEFAULT = 0;
           #endregion

           #region Static

           #region NativeMethods
           [DllImport("advapi32.dll", CharSet = CharSet.Auto)]
           private static extern int LogonUser(String UserName,
                                              String Domain,
                                              String Password,
                                              int LogonType,
                                              int LogonProvider,
                                              ref IntPtr Token);

           #endregion

           #region Methods
           public static int LogOnUser(String userName, String domain, String password)
           {
               IntPtr token = IntPtr.Zero;
               return LogonUser(userName, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref token);
           }
           #endregion
           #endregion
       }

2.Create the service proxy from the Silverlight application and call the Authentication method described in the WCF service

Silverlight Code behind

UserService.UserClient Proxy = new UserService.UserClient();
Proxy.AuthenticateUserCompleted += 
    new EventHandler<UserService.AuthenticateUserCompletedEventArgs>(Proxy_AuthenticateUserCompleted);
Proxy.AuthenticateUserAsync(txtUser.Text, txtPassword.Password);

void Proxy_AuthenticateUserCompleted(object sender, UserService.AuthenticateUserCompletedEventArgs e)
       {
           MessageBox.Show(e.Result.Equals(true) ? "login succeeded" : "login failed");
       }