Recently Microsoft has updated the ASP.NET MVC to Beta status, and along with that came code changes. One of the code changes to the IModelBinder and how it interacts with the Parameter bindings broke what I wrote on the last post (utilizing ASP.NET MVC as a JSON Service Provider, and coding the entire web site on the client side). Upon loading the Beta bits, I realized my AJAX Parameter function was infinite looping. The reason is that the Model Binder defaults to trying to bind Complex Types in the Action Parameter to the form values being passed back, however, since I am not doing a form postback, it could not bind that to the complex type, and could not run the ActionExecuting on the AjaxParameterAttribute I had set. Here is the changes along with testing Dates and the Microsoft Client Side Ajax Templating Engine.