C# 4.0 Features

• By Troy Magennis
• Mar 9, 2010

This chapter is from the book

LINQ to Objects Using C# 4.0: Using and Extending LINQ to Objects and Parallel LINQ (PLINQ)

Goals of this chapter:

• Define new C# 4.0 language features.
• Demonstrate the new language features in the context of LINQ to Objects.

C# is an evolving language. This chapter looks at the new features added into C# 4.0 that combine to improve code readability and extend your ability to leverage LINQ to Object queries over dynamic data sources. The examples in this chapter show how to improve the coding model for developers around reading data from various sources, including text files and how to combine data from a COM-Interop source into a LINQ to Objects query.

Evolution of C#

C# is still a relatively new language (circa 2000) and is benefiting from continuing investment by Microsoft's languages team. The C# language is an ECMA and ISO standard. (ECMA is an acronym for European Computer Manufacturers Association, and although it changed its name to Ecma International in 1994, it kept the name Ecma for historical reasons.¹) The standard ECMA-334 and ISO/IEC 23270:2006 is freely available online at the Ecma International website² and describes the language syntax and notation. However, Microsoft's additions to the language over several versions take some time to progress through the standards process, so Microsoft's release cycle leads Ecma's acceptance by at least a version.

Each version of C# has a number of new features and generally a major theme. The major themes have been generics and nullable types in C# 2.0, LINQ in C# 3.0, and dynamic types in C# 4.0. The major features added in each release are generally considered to be the following:

• C# 2.0—Generics (.NET Framework support was added, and C# benefited from this); iterator pattern (the yield keyword); anonymous methods (the delegate keyword), nullable types, and the null coalescing operator (??).
• C# 3.0—Anonymous types, extension methods, object initializers, collection initializers, implicitly typed local variables (var keyword), lambda expressions (=>), and the LINQ query expression pattern.
• C# 4.0—Optional Parameters and Named Arguments, Dynamic typing (dynamic type), improved COM-Interop, and Contra and Co-Variance.

The new features in C# 3.0 that launched language support for LINQ can be found in Chapter 2, "Introducing LINQ to Objects," and this chapter documents each of the major new features in C# 4.0 from the perspective of how they impact the LINQ story.