What's New in C#7, C#8 and C#9

This short course covers the latest and greatest features of C#, covering versions 7, 7.1, 7.2, 7.3, 8.0 and 9.0 of the language that are being sim-shipped with corresponding Visual Studio updates.

Course Topics

Here's every language feature presented in this course, grouped by the version of the C# language.

C# 7:

• Out Variables

• Pattern Matching (is and switch expressions)

• Tuples and Tuple Deconstruction

• Local Functions

• Ref Returns and Locals

• Expression Bodied Members

• Throw Expressions

• Generalized Async Return Types

• Literal Improvements

C# 7.1:

• How to turn on C# 7.1 support

• Async Main

• Default Expressions

• Ref Assemblies

• Infer Tuple Names

• Pattern-Matching with Generics

C# 7.2:

• Leading Digit Separators

• 'Private Protected' Access Modifier

• Non-Trailing Named Arguments

• Reference Semantics on Value Types:

  • 'In' Parameters

  • 'Ref Readonly' Variables

  • 'Ref Struct' and Span<T>

C# 7.3:

• Performance improvements

  • Access fixed fields without pinning

  • Reassign ref local variables

  • Use initializers on stackalloc arrays 

  • Use fixed statements on any type that supports a pattern 

• Enhancements to existing features 

  • Tuple == and != support 

  • Use expression variables in more locations 

  • Attach attributes to backing field of auto-properties 

  • Improved method resolution when arguments differ by 'in' 

  • Improved overload resolution 

• New compiler options: 

  • deterministic

  • publicsign

  • pathmap

C# 8:

• Nullable Reference Types

• Indices and Ranges

• Default Interface Members

• Pattern Matching

C# 9:

• Record Types

• Top-Level Calls

• Initial Setters

• Pattern Matching Improvements (type patterns, parenthesized patterns, conjunctive and, disjunctive or, negated not, relational patterns)

• Performance and Interop (Native sized integers (nint/nuint), function pointers, SkipLocalsInit)

• Fit and Finish (target-typed new, target type resolution of conditional expressions, static modifier for lambda expressions and anonymous methods, covariant return types, foreach GetEnumerator() use, discards as parameters to lambdas, attributes on local functions)

• C# Code Generators (partial method syntax, module initializers)

Prerequisites

• Knowledge and understanding of C# 6 and earlier

• General experience in .NET/C# application development

Learning Outcomes

• An understanding and appreciation of latest C# 7/7.1/7.2/7.3/8/9 language features

• Understanding of how to convert existing C# code to C# 7/7.1/7.2/7.3/8/9