C# in Depth

LINQ beyond .NET 3.5345Listing 12.19Querying Amazon’s web service with LINQAmazonBookSearch source = new AmazonBookSearch();var webQuery = from book in sourcewhere book.Title.Contains("LINQ")select book;CCreates providerB with your access IDCreates queryfor web servicevar query = from book in webQuery.AsEnumerable()orderby book.Year, book.Titleselect book;DPerforms moreoperations in memoryforeach (AmazonBook book in query){Console.WriteLine ("{0}: {1}", book.Year, book.Title);}I’ve taken Fabrice’s provider and tweaked it slightly so that we can pass our own AmazonAccess ID into the provider’s constructor B. The source is part of the Visual Studio2008 solution containing the examples for this chapter.You may be slightly surprised to see two query expressions in listing 12.19. As aproof of concept, the LINQ to Amazon provider only allows a limited number ofoperations, not including ordering. We use the web query C as the source for anin-memory LINQ to Objects query expression D. The web service call still only takesplace when we start executing the query E, due to the deferred execution approachtaken by LINQ.The output at the time of this writing is included here. By the time you read this, Iexpect the list may be considerably longer.1998: A linq between nonwovens and wovens. (...)2007: Introducing Microsoft LINQ2007: LINQ for VB 20052007: LINQ for Visual C# 20052007: Pro LINQ: Language Integrated Query in C# 20082008: Beginning ASP.NET 3.5 Data Access with LINQ , C# (...)2008: Beginning ASP.NET 3.5 Data Access with LINQ, VB (...)2008: LINQ in Action2008: Professional LINQE Executesquery,displaysresultsEven though LINQ to Amazon is primitive, it demonstrates an important point: LINQis capable of more than just database and in-memory queries. Our next providerproves that even when it’s talking to databases, there’s more to LINQ than just LINQto SQL.LINQ TO NHIBERNATENHibernate is an open source ORM framework for .NET, based on the Hibernateproject for Java. It supports textual queries in its own query language (HQL) and alsoa more programmatic way of building up queries—the Criteria API.Prolific blogger and NHibernate contributor Ayende 6 has initiated a LINQ to NHibernateprovider that converts LINQ queries not into SQL but into NHibernate Criteriaqueries, taking advantage of the SQL translation code in the rest of the project. Aside6www.ayende.com/Blog/Licensed to Rhona Hadida