Authenticate User Active Directory Credentials in C#

public static bool AuthenticateAD(string username, string password)
{
    using(var context = new PrincipalContext(ContextType.Domain, "DOMAIN"))
    {
        return context.ValidateCredentials(username, password);
    }
}

// using sAMAccountName version of username:
if (AuthenticateAD("DOMAIN\\username", "pass"))
{
    Console.WriteLine("Authenticated");
}

// using UPN version of username:
if (AuthenticateAD("username@DOMAIN.net", "pass"))
{
    Console.WriteLine("Authenticated");
}