SL3+RIA Services: what assembly is required to use InvokeOperation<Type>?

Background: My experience in C# / Silverlight / .Net development is about 4 weeks worth.

The official documentation for .Net RIA Services July 2009 Preview, on Page 66 Section 6.2.2.2 states how one would consume the result of a call made on a function marked as [ServiceOperation]. This examples specifically uses 'InvokeOperation' (as does many examples i have found in search for an answer to my question). I use Web Developer Express开发者_如何学JAVA 2008 and when i use 'InvokeOperation' i get "The type or namespace name 'InvokeOperation' could not be found...". Please note i have Googled this but with my little knowledge i believe i am not using the correct search criteria.

My question thus: What assembly should i reference or what should be added as 'using' in my class to enable me to use 'InvokeOperation' in my SL3+RIA Services solution?

Thank you for your assistance in advance.

[ServiceOperation] (in the July CTP) got renamed to [Invoke] (in the PDC drop) The breaking changes doc can be found here - http://code.msdn.microsoft.com/RiaServices/Release/ProjectReleases.aspx?ReleaseId=3570

In Silverlight 4 with the latest RIA services preview it is:

System.ServiceModel.DomainServices.Client

found it: "using System.Windows.Ria.Data;"