Introduction to Language‐Integrated Query (LINQ)

The Language‐Integrated Query (LINQ) pattern is established on the basis of a group of methods called standard query operators (SQOs). Most of these methods operate on sequences, where a sequence is an object whose type implements the IEnumerable interface or the IQueryable interface. LINQ can be considered as a converter or bridge that sets up a mapping relationship between the abstract objects implemented in SQOs and the physical relational databases implemented in the real world. LINQ is composed of three major components: LINQ to Objects, LINQ to ActiveX Data Object (ADO).NET, and LINQ to XML. LINQ to Objects is used to query any sequences or collections that are either explicitly or implicitly compatible with IEnumerable sequences or IENumerable collections. LINQ to DataSet is a subcomponent of LINQ to ADO.NET. LINQ to Entities belongs to LINQ to ADO. NET and it is a subcomponent of LINQ to ADO.NET.