AJAX request to WCF from ExtJS 4 client

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WCF

ExtJS

ASP.NET4

hello everyone,
I need some help.I am developing an application architecture using Asp.Net,
WCF,ExtJS 4.Till now the application works like this:

1) extjs client sends ajax request to asp.net handler file(.ashx file), the
2) handler calls WCF service, then
3) WCF sends back c# object to the handler, then
4) handler converts the c# object into json format and returns it as a response to the ajax call.

Everything works fine. Now i want some changes,i need to be able to call WCF services directly from ExtJS client.How do i achieve this?