What’s New With .NET 8 and C# 12

.NET 8.0: Full Summary of What’s New

.NET 8 brings significant improvements and new features across performance, developer productivity, cloud-native development, AI integration, and cross-platform capabilities. Below is a comprehensive summary of the most important updates.

Major Highlights

.NET 8.0 includes improvements for:

• Performance with substantial runtime and library optimizations, including a new Dynamic Profile-Guided Optimization (PGO) code generator, which can boost app performance by up to 20% ^{1 2 3}.
• Cloud-Native Development with the introduction of .NET Aspire, a new stack for building observable, production-ready cloud-native applications with improved local developer experience¹.
• Containerization to produce smaller, more secure container images with non-root user support, enabling faster and safer deployments¹.
• Native AOT (Ahead-of-Time) Compilation to enhance support for compiling apps to native code, reducing memory usage, improving startup times, and eliminating the need for JIT at runtime^{1 4}.
• AI Integration with easier integration with AI services and plugins, including improved System.Numerics and collaboration with Azure OpenAI¹.

Key Features and Improvements

On the performance and diagnostics side, .NET 8.0 adds:

• Dynamic PGO for smarter code optimization¹.
• Faster application startup and reduced memory usage.
• Improved diagnostics and observability tools for easier monitoring, profiling, and debugging⁴.

It comes with C# 12 Language Features:

• Primary constructors for all classes and structs, simplifying object initialization.
• Default values for lambda expression arguments.
• Type aliasing for any type, not just named ones⁴¹.
• Enhanced pattern matching and other expressiveness improvements^{4 5}.

I’ll detail them below with examples.

Garbage Collection and Memory Management receive updates:

• with new dynamic memory limits for the garbage collector, especially useful for cloud and Kubernetes scenarios⁴.
• with an API for refreshing memory limits at runtime.

JSON Handling gets better with:

• Faster and more standards-compliant JSON serialization/deserialization (RFC 8259, ECMA-404)⁶.
• Support for property serialization from interface hierarchies.
• New attributes for stricter JSON mapping with better error handling^{4 6}.

Regarding ASP.NET Core 8, the frontend solution of Microsoft,

• We see up to 18% faster than .NET 7 for web workloads⁴.
• We receive Native AOT support for web apps.
• We can enjoy enhanced Blazor with Full-stack Blazor for unified web UI development, improved server-side rendering, and better interactivity^{4 1 7}.
• And finally, APIs for metrics, dependency injection, and cloud readiness receive improvements over the previous version ^{7 6}.

With Entity Framework Core 8, support for complex/value type support (e.g., Address, Coordinate) is introduced. Also, lazy loading, no-tracking queries, JSON column mapping, and model building receive performance boost ^{3 4}.

On the cross-platform framework .NET MAUI for native-ready applications, .NET 8.0 brings better controls, gesture recognizers, navigation, and platform integration. On the DX side, performance enhancements for cross-platform (Windows, macOS, Android, iOS) app development^{3 4}.

For better control over time and faking values, this .NET version introduces a new TimeProvider class and ITimer interface⁴.

On the cryptography side, it adds SHA-3 support for enhanced security and improves the randomness APIs (e.g., GetItems(), Shuffle()), useful for secure and unbiased data handling⁴⁶.

Feature Comparison Table

C# 12 New Coding Features with Examples

It introduces several new language features⁸ that enhance expressiveness and reduce boilerplate. Here are some of the most notable additions, each with a code example.

Primary Constructors for Classes and Structs

Primary constructors allow you to declare constructor parameters directly in the class or struct declaration, simplifying property initialization.

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public class Employee(string firstName, string lastName, DateTime hireDate, decimal salary)
{
    public string FirstName { get; init; } = firstName;
    public string LastName { get; init; } = lastName;
    public DateTime HireDate { get; init; } = hireDate;
    public decimal Salary { get; init; } = salary;
}

This reduces boilerplate and makes your classes more concise^{9 10}.

Default Values for Lambda Expression Parameters

You can now specify default parameter values in lambda expressions, similar to regular methods.

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Func add = (x, y = 5) => x + y;

Console.WriteLine(add(10));    // Output: 15 (y defaults to 5)
Console.WriteLine(add(10, 20)); // Output: 30 (y is 20)

This makes lambdas more flexible and concise^{11 12 8}.

Alias Any Type

You can now create aliases not just for named types, but for any type, including tuples, arrays, and more.

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using Person = System.Collections.Generic.Dictionary;

Person p = new Person();
p["Name"] = "Alice";
p["Age"] = 25;

This helps with code readability and reuse¹³.

Collection Expressions

C# 12 introduces collection expressions for easier array and collection initialization and merging.

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int[] part1 = [1, 2, 3];
int[] part2 = [4, 5, 6];
int[] combined = [.. part1, .. part2];

foreach (var number in combined)
    Console.Write($"{number} "); // Output: 1 2 3 4 5 6

This syntax is concise and expressive for collection manipulation¹².

Pattern Matching Enhancements

The pattern matching is now more powerful, enabling property patterns, relational patterns, and negation directly in conditions.

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// Property patterns in switch
switch (shape)
{
    case Circle { Radius: var radius }:
        Console.WriteLine($"Radius: {radius}");
        break;
    case Rectangle { Width: var width, Height: var height }:
        Console.WriteLine($"Width: {width}, Height: {height}");
        break;
}

// Relational patterns
if (value is >= 10 and <= 20)
{
    // value is between 10 and 20 inclusive
}

// Negation patterns
if (shape is not Circle)
{
    // shape is not a Circle
}