DataTable to JSON
Would it help you convince your bosses to install a library if it's Microsoft's AJAX extensions for .NET 2.0?
Included in them is System.Web.Script.Serialization.JavascriptSerializer, which is used in Step 4 of the last link in your post.
Hey budy, its is all here in Rick's blog post Serializing DataTable using Json.NET. He explains in detail how you can accomplish it using Json.NET from James Newton King.