MVC3: Use of ActionMethodSelectorAttribute causes HttpPostAttribute to be ignored
public class AjaxRequestAttribute : ActionMethodSelectorAttribute
{
    public override bool IsValidForRequest(ControllerContext controllerContext, System.Reflection.MethodInfo methodInfo)
    {
        return controllerContext.HttpContext.Request.IsAjaxRequest();
    }
}

[AjaxRequest]
public ActionResult Login()
{
     ...
}

[HttpPost, AjaxRequest]
public ActionResult Login(LoginModel model, string returnUrl)
{
    ...
}

public class AjaxPostRequestAttribute : HttpPostAttribute
{
    public override bool IsValidForRequest(
        ControllerContext controllerContext, MethodInfo methodInfo)
    {
        var isHttpPost = base.IsValidForRequest(controllerContext, methodInfo);
        return isHttpPost
            && controllerContext.HttpContext.Request.IsAjaxRequest();
    }
}

[AjaxPostRequest]
public ActionResult Login(LoginModel model, string returnUrl)
{
    ...
}

public class AjaxGetAttribute : ActionMethodSelectorAttribute
{
    public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo)
    {
        var isHttpGet = new AcceptVerbsAttribute(HttpVerbs.Get).IsValidForRequest(controllerContext, methodInfo);
        return isHttpGet && controllerContext.HttpContext.Request.IsAjaxRequest();
    }
}

public class AjaxPostAttribute : ActionMethodSelectorAttribute
{
    public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo)
    {
        var isHttpPost = new AcceptVerbsAttribute(HttpVerbs.Post).IsValidForRequest(controllerContext, methodInfo);
        return isHttpPost && controllerContext.HttpContext.Request.IsAjaxRequest();
    }
}