CIL is the object-oriented assembly language used by.NET Framework (pronounced “dot net”) is a free development framework on Windows, widely used to build applications and services with simple programming model and great productivity.NET Framework is based on Common Intermediate Language (CIL), and consists of Common Language Runtime (CLR), Framework Class Library (FCL): NET family, which enable C# and LINQ to work on many platforms.NET Framework There are also many other frameworks joins the. Since then, many functional features including LINQ has been built into C# language and. In 2002, C# was initially introduced with. The contents was initially based on my LINQ via C# talks. This is a tutorial of functional programming and LINQ in C# language.