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C# language versions and features

If you already have some familiarity with older versions of C# and are excited to find out about the new features in the most recent versions of C#, then I have made it easier for you to jump around by listing language versions and their important new features below, along with the chapter number and topic title where you can learn about them.

Project COOL

Before the first release of C#, it had the codename C-like Object-Oriented Language (COOL).

C# 1, February 2002

Included all the important features of a statically typed object-oriented modern language, as you will see throughout Chapters 2 to 6.

C# 1.2, 2003

A few minor improvements, like automatic disposal at the end of foreach statements, was released with Visual Studio .NET 2003.

C# 2, 2005

Enabled strong data typing using generics, to improve code performance and reduce type errors, including the topics listed in Table 2.1:

Feature Chapter Topic
Nullable value types 6 Making a value type nullable
Generics 6 Making types more reusable with generics

Table 2.1: Features of C# 2 covered in this book

C# 3, 2007

Enabled declarative coding with Language INtegrated Queries (LINQ) and related features like anonymous types and lambda expressions, including the topics listed in Table 2.2:

Feature Chapter Topic
Implicitly typed local variables 2 Inferring the type of a local variable
LINQ 11 All topics in Chapter 11, Querying and Manipulating Data Using LINQ

Table 2.2: Features of C# 3 covered in this book

C# 4, 2010

Improved interoperability with dynamic languages like F# and Python, including the topics listed in Table 2.3:

Feature Chapter Topic
Dynamic types 2 Storing dynamic types
Named/optional arguments 5 Optional parameters and named arguments

Table 2.3: Features of C# 3 covered in this book

C# 5, 2012

Simplified asynchronous operation support by automatically implementing complex state machines while writing what looks like synchronous statements, including the topics listed in Table 2.4:

Feature Chapter Topic
Simplified asynchronous tasks 2 Understanding async and await

Table 2.4: Features of C# 5 covered in this book

C# 6, 2015

Focused on minor refinements to the language, including the topics listed in Table 2.5:

Feature Chapter Topic
static using imports 2 Simplifying the usage of the console
Interpolated strings 2 Displaying output to the user
Expression-bodied members 5 Defining read-only properties

Table 2.5: Features of C# 6 covered in this book

C# 7, March 2017

Added functional language features like tuples and pattern matching, as well as minor refinements to the language, including the topics listed in Table 2.6:

Feature Chapter Topic
Binary literals and digit separators 2 Storing whole numbers
Pattern matching 3 Pattern matching with the if statement
out variables 5 Controlling how parameters are passed
Tuples 5 Combining multiple values with tuples
Local functions 6 Defining local functions

Table 2.6: Features of C# 7 covered in this book

C# 7.1, August 2017

Focused on minor refinements to the language, including the topics listed in Table 2.7:

Feature Chapter Topic
async Main 2 Improving responsiveness for console apps
Default literal expressions 5 Setting fields with default literals
Inferred tuple element names 5 Inferring tuple names

Table 2.7: Features of C# 7.1 covered in this book

C# 7.2, November 2017

Focused on minor refinements to the language, including the topics listed in Table 2.8:

Feature Chapter Topic
Leading underscores in numeric literals 2 Storing whole numbers
Non-trailing named arguments 5 Optional parameters and named arguments
private protected access modifier 5 Understanding access modifiers
You can test == and != with tuple types 5 Comparing tuples

Table 2.8: Features of C# 7.2 covered in this book

C# 7.3, May 2018

Focused on performance-oriented safe code, which improved ref variables, pointers, and stackalloc. These features are advanced and rarely needed by most developers, so they are not covered in this book.

C# 8, September 2019

Introduced a major change to the language related to null handling, including the topics listed in Table 2.9:

Feature Chapter Topic
Switch expressions 3 Simplifying switch statements with switch expressions
Nullable reference types 6 Making a reference type nullable
Default interface methods 6 Understanding the default interface methods

Table 2.9: Features of C# 8 covered in this book

C# 9, November 2020

Introduced record types, refinements to pattern matching, and minimal-code projects, including the topics listed in Table 2.10:

Feature Chapter Topic
Minimal-code console apps 1 Understanding top-level programs
Target-typed new expressions 2 Using target-typed new expressions to instantiate objects
Enhanced pattern matching 5 Pattern matching with objects
Records 5 Working with records

Table 2.10: Features of C# 9 covered in this book

C# 10, November 2021

Focused on features that minimize the amount of code needed in common scenarios, including the topics listed in Table 2.11:

Feature Chapter Topic
Global namespace imports 2 Importing namespaces
Constant string literals 2 Formatting using interpolated strings
File-scoped namespaces 5 Simplifying namespace declarations
Record structs 6 Working with record struct types
ArgumentNullException.ThrowIfNull 6 Checking for null in method parameters

Table 2.11: Features of C# 10 covered in this book

C# 11, November 2022

Focused on features that simplify your code, including the topics listed in Table 2.12:

Feature Chapter Topic
Raw string literals 2 Understanding raw string literals
Line breaks in interpolated string expressions 2 Formatting using interpolated strings
Required properties 5 Requiring properties to be set during instantiation

Table 2.12: Features of C# 11 covered in this book

C# 12, November 2023

Focused on features that simplify your code and improving performance, including the topics listed in Table 2.13:

Feature Chapter Topic
Inline arrays 3 Understanding inline arrays
Default lambda parameters 4 Lambda expressions with default parameter values
New exception guard clauses 4 Throwing exceptions using guard clauses
Aliasing any type 5 Renaming a type with a using alias
Primary constructors 5 Defining a primary constructor
Interceptors 7 Method interceptors

Table 2.13: Features of C# 12 mentioned in this book

More Information, The history of C#: https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-version-history