JSON XSS Exploit

I read this great article at http://www.microsoft.com/en-gb/developers/articles/week02feb14/defence-mechanisms-in-asp-net-that-protect-against-cross-site-scripting-attacks

The article details how Request Validation is bypassed when using a type of JSON post in AJAX.

We recently had an exploit revealed in one of our ASP.NET application that uses this same trick to bypass request validation.

Is there a way to check / trap in code or some other mechanism to prevent this type of exploit using JSON?