WCF web services, JSON and Membership/Roles issue

We write a WCF web service. How can we call it's methods in JSON format? An additional issue is how can we secure our web service开发者_高级运维s. I'd like to use Microsoft Membership and Roles providers for users authentication and authorization. The question is how to do this. Is it possible to do authentication and authorization behind-the-scenes (in context of WCF), or I must call ValidateUser() and IsUserInRole() in every web method for every user call? Whether I restricted to use webHttpBinding (over wsHttpBinding) because our client-side programmer familiar with AJAX/JSON? Whether there are any restrictions of webHttpBinding concerning using Membership/Roles comparably comparably to wsHttpBinding?

Thanks a lot in advance!

Ilan.