LINQ is an acronym for Language Integrated Query, and supported by C# and VB.NET. It can be used to query many different types of data, including relational, XML, and even objects. Another way to describe LINQ is that it is programming language syntax that is used to query data.
Types of LINQ -
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Also, You can write LINQ queries in C# for any collection of objects that supports IEnumerable or the generic IEnumerable interface. LINQ support is also provided by third parties for many Web services and other database implementations.