Page 177 - CSharp/C#

Chapter 25: C# 6.0 Features

Introduction

This sixth iteration of the C# language is provided by the Roslyn compiler. This compiler came out
with version 4.6 of the .NET Framework, however it can generate code in a backward compatible
manner to allow targeting earlier framework versions. C# version 6 code can be compiled in a fully
backwards compatible manner to .NET 4.0. It can also be used for earlier frameworks, however
some features that require additional framework support may not function correctly.

Remarks

The sixth version of C# was released July 2015 alongside Visual Studio 2015 and .NET 4.6.

As well as adding some new language features it includes a complete rewrite of the compiler.
Previously csc.exe was a native Win32 application written in C++, with C# 6 it is now a .NET
managed application written in C#. This rewrite was known as project "Roslyn" and the code is
now open source and available on GitHub.

Examples

Operator nameof

The nameof operator returns the name of a code element as a string. This is useful when throwing
exceptions related to method arguments and also when implementing INotifyPropertyChanged.

public string SayHello(string greeted)
{
if (greeted == null)
throw new ArgumentNullException(nameof(greeted));

Console.WriteLine("Hello, " + greeted);
}

The nameof operator is evaluated at compile time and changes the expression into a string literal.
This is also useful for strings that are named after their member that exposes them. Consider the
following:

public static class Strings
{
public const string Foo = nameof(Foo); // Rather than Foo = "Foo"
public const string Bar = nameof(Bar); // Rather than Bar = "Bar"
}

Since nameof expressions are compile-time constants, they can be used in attributes, case labels,
switch statements, and so on.

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