该文请参考 http://www.west-wind.com/WebLog/posts/310747.aspx
If you've been thinking about using ASP.NET Ajax in combination with WCF, life got a lot easier with .NET 3.5 and the new REST support. The webHttp binding along with the ASP.NET AJAX specific version makes it easy to use WCF instead of ASMX services with ASP.NET AJAX.
A valid question to ask though is: Do I need to use WCF or should I continue to use ASMX?
If ASMX services are working fine for you as is with MS AJAX you probably don't have to switch. In fact if your services are purely based on making AJAX callbacks from a pure Web app and you don't plan on reusing existing services, there's not much of an advantage using WCF over ASMX services. ASMX services continue to be easier to set up and work with and maybe more importantly they don't require .NET 3.5.
WCF REST services however provide features that ASMX does not, such as the ability to serve raw non-ASP.NET AJAX formatted data in 'bare' format. If you're working with non-ASP.NET AJAX clients like jQuery or Prototype this can be a bonus and lets you avoid using the MS AJax client libraries and ScriptManager. WCF REST also supports raw XML based access to services which is also useful and can't be directly accomplished with ASMX.
Another consideration: If you have existing services that rely on HttpContext, realize that WCF by default doesn't support access to the underlying 'host platform'. WCF is supposed to be host agnostic and WCF services can in fact be running outside of IIS. If you have existing code that relies on HttpContext access to the Request or Session object which is common , it's probably best to leave it in ASMX (although WCF has a way to do that as well).
But if you're starting a new app and you're using .NET 3.5 on the server anyway you might as well take advantage of WCF's REST/Ajax features and the wider range of options available to publish data.
WCF REST Configuration for ASP.NET AJAX and plain REST Services
