A sample authentication interceptor for Nancy using Castle Interceptors for AOP

AuthenticationInterceptor.cs

public class AuthenticationInterceptor : IInterceptor
{
    bool CanIntercept(IInvocation invocation) { return invocation.Method.GetCustomAttributes(true).Any(a => a is RequiresAuthenticationAttribute); }

    public void Intercept(IInvocation invocation)
    {
        if (!CanIntercept(invocation)) invocation.Proceed();
        else
        {
            var module = invocation.InvocationTarget as NancyModule;
            try
            {
                if (module.Request.Query.api_key == "Password")
                    invocation.Proceed();
                else
                    invocation.ReturnValue = new Response { StatusCode = HttpStatusCode.Unauthorized };
            }
            catch (RuntimeBinderException)
            {
                invocation.ReturnValue = new Response { StatusCode = HttpStatusCode.Unauthorized };
            }
        }
    }
}