Working with JSON on the Server-Side in ASP.NET and C#

I have an ASP.NET web form that is using JQuery on the client-side. I have a user interface that is building a collection of objects and storing them in JSON. With my client-side implementation complete, I need to now work with that information when the user clicks a button. When this button is clicked, I need to loop through that JSON collection and validate the entries. My problem is, I’m not sure how to do it.