1: Linq to Xml namespace System.Xml.Linq
2：Linq to Objects
3：Linq to Entities
Linq to Objects and Linq to Entities of Where's Where the two classes are System.Core program System.Linq namespace concentrated.
Which method you choose to use the compiler. Expression Type what purpose. <Func <TSource, bool >> parameters are passed either by Func <TSource, bool> parameter passing, or use Expression, lambda expressions are the same, just different compiler behavior.
It is selected according to the source parameter. The method of best matching parameter selected according to the compiler.
CreateQuery ObjectContext classes defined in the Ado.Net Entity Framework <T> () method returns an implementation of IQueryable <TSource> ObjectQuery <T> object interface, so use Entity FrameWork the Where () method Queryable class.
Summary: Use parallel Linq easily parallelized long-running queries.
Expression tree allows queries against the data source during the operation member. Because concentrated expression in the program memory.
There are many third-party providers, such as Linq to MySql, Linq to Amazon, Linq to Flickr, Linq to LDAP, Linq to SharePoint.
ExpressionType