Explore the Key Features of .NET 9

Article

Microsoft’s release of .NET 9 continues its mission to enhance the developer experience, optimize performance, and expand its feature set for modern application development. Whether you’re a seasoned .NET developer or just starting, the updates in .NET 9 bring powerful capabilities to streamline workflows, improve cross-platform support, and elevate application performance.

In this article, we’ll explore the key features of .NET 9 and dive into practical code examples to help you leverage its full potential.

Key Highlights of .NET 9

Native AOT (Ahead-of-Time) Compilation Enhancements
Improved JSON Serialization with Source Generators
C++ Interoperability Improvements
Linux and ARM64 Optimization
Modern Web Development with Minimal APIs
Performance and Security Enhancements

1. Native AOT (Ahead-of-Time) Compilation Enhancements

Native AOT continues to evolve in .NET 9, enabling developers to compile applications into self-contained executables optimized for performance and reduced size. This is particularly beneficial for microservices, CLI tools, and serverless applications, where startup time and memory footprint are critical.

Key Benefits

Smaller executables with no runtime dependencies.
Faster startup time compared to JIT-compiled applications.
Improved diagnostics support for debugging AOT-compiled apps.

Example

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello from .NET 9 with Native AOT!");
    }
}

Building for Native AOT

dotnet publish -r win-x64 -c Release /p:PublishAot=true

2. Improved JSON Serialization with Source Generators

Serialization has always been a cornerstone of .NET development. In .NET 9, the JSON source generator enhancements deliver better performance and type safety, reducing the runtime overhead of serialization and deserialization.

Key Features

Improved performance: Faster and more efficient serialization.
Compile-time checks: Detect issues earlier in the development lifecycle.
Support for polymorphic types.

Example

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

[JsonSerializable(typeof(User))]
public partial class UserJsonContext : JsonSerializerContext
{
}

public class User
{
    public string Name { get; set; }
    public int Age { get; set; }
}

// Serialize and Deserialize
var user = new User { Name = "John", Age = 28 };
string json = JsonSerializer.Serialize(user, UserJsonContext.Default.User);

var deserializedUser = JsonSerializer.Deserialize<User>(json, UserJsonContext.Default.User);

Console.WriteLine(deserializedUser.Name);

3. C++ Interoperability Improvements

For developers working with legacy C++ libraries or requiring low-level performance optimizations, .NET 9 enhances the interop layer, making it easier to call C++ libraries from managed code.

Key Improvements

Enhanced support for memory pinning and marshaling.
Optimized interop scenarios for cross-platform compatibility.

Example

using System;
using System.Runtime.InteropServices;

[DllImport("native.dll", EntryPoint = "Add")]
public static extern int Add(int a, int b);

class Program
{
    static void Main()
    {
        int result = Add(5, 10);
        Console.WriteLine($"Result from native library: {result}");
    }
}

4. Linux and ARM64 Optimizations

As cloud-native and containerized applications become the norm, .NET 9 introduces optimizations for Linux and ARM64 platforms. These updates ensure smoother deployments and better performance in modern cloud environments.

Key Enhancements

Reduced startup time for Linux-based containerized applications.
Improved ARM64 support for energy-efficient workloads.
Smaller base images for containerized applications.

Dockerfile Example

ROM mcr.microsoft.com/dotnet/runtime:9.0

WORKDIR /app

COPY . .

ENTRYPOINT ["dotnet", "MyApp.dll"]

5. Modern Web Development with Minimal APIs

Minimal APIs, introduced in .NET 6, continue to evolve in .NET 9, offering even greater flexibility and simplicity for building lightweight web services.

Example. Building a Minimal API

var builder = WebApplication.CreateBuilder(args);

var app = builder.Build();



app.MapGet("/", () => "Welcome to .NET 9!");

app.MapPost("/api/data", (DataModel data) => Results.Ok(data));



app.Run();



record DataModel(string Name, int Value);

Publishing for Production

dotnet publish -c Release -o ./publish

6. Performance and Security Enhancements

Performance is a hallmark of every .NET release, and .NET 9 is no exception. Developers can expect faster execution, improved garbage collection, and better threading.

Key Improvements

Garbage Collection (GC): Reduced pauses and improved memory management.
HTTP/3 Enhancements: Lower latency and faster handshakes for web apps.
Security Updates: Improved cryptographic support and hardened runtime defenses.

Benchmarking Example

Using System.Diagnostics to measure performance:

using System.Diagnostics;



var sw = Stopwatch.StartNew();

// Perform a task

sw.Stop();

Console.WriteLine($"Elapsed time: {sw.ElapsedMilliseconds}ms");

Detailed Use Cases

1. Building Cloud-Native APIs

The cloud-native focus in .NET 9 makes it easier to integrate with Kubernetes and observability tools like OpenTelemetry.

using OpenTelemetry.Trace;



var builder = WebApplication.CreateBuilder(args);



builder.Services.AddOpenTelemetryTracing(traceBuilder =>

{

    traceBuilder

        .AddAspNetCoreInstrumentation()

        .AddConsoleExporter();

});



var app = builder.Build();

app.MapGet("/", () => "Cloud-Native App with OpenTelemetry in .NET 9");

app.Run();

2. Serverless Applications

Deploy AOT-compiled applications for serverless environments to minimize cold start latency.

// Native AOT optimizes cold start times

Console.WriteLine("Optimized for serverless in .NET 9!");

Why Upgrade to .NET 9?

Performance Boost: Applications run faster with reduced memory consumption.
Simplified Development: Minimal APIs and improved tooling streamline the coding experience.
Future-Ready: Optimized for cloud-native, cross-platform, and microservices architectures.

Conclusion

.NET 9 is a robust release packed with features that cater to modern development challenges. From Native AOT to JSON source generator improvements, the platform empowers developers to create fast, secure, and scalable applications. By embracing .NET 9, you’re not only improving your application’s performance but also ensuring long-term compatibility with emerging technologies.

Start experimenting with .NET 9 today to unlock its full potential in your projects! For more information, visit the official Microsoft .NET documentation.