What's new in .NET 10 and C# 14

Discover the most important changes in .NET 10 LTS, focusing on runtime improvements, ASP.NET Core, MAUI, and detailed C# 14 enhancements with examples.

.NET 10 is here as a Long-Term Support (LTS) release, offering stability, performance improvements, and a number of developer-focused enhancements. It provides an excellent foundation for both new projects and long-term production environments. In this article, we’ll focus on the runtime and libraries, ASP.NET Core, MAUI, and the most significant updates in C# 14, including practical examples that make these features immediately useful.

Runtime and libraries

The .NET 10 runtime introduces optimizations that improve performance in everyday applications. Key improvements include JIT inlining, method devirtualization, and stack allocation enhancements. AVX10.2 support and NativeAOT enhancements make it easier to generate high-performance native binaries.

The .NET libraries have also been improved across areas like cryptography, serialization, collections, and networking. JSON serialization now supports disallowing duplicate properties, strict modes, and PipeReader integration for better efficiency. Networking sees new tools like WebSocketStream for simplified WebSocket communication and TLS 1.3 support on macOS.

These changes may seem low-level, but they directly impact the responsiveness, memory usage, and reliability of your applications, especially in high-load or real-time scenarios.

ASP.NET Core 10

ASP.NET Core 10 continues to polish the developer experience. Blazor improves with WebAssembly preloading and automatic memory pool eviction. Minimal APIs are more robust, diagnostics are clearer, and form validation is more consistent. Identity now supports passkeys, aligning with modern authentication trends.

For developers building web applications or APIs, these enhancements make it easier to write fast, secure, and maintainable code without wrestling with boilerplate or low-level optimizations.

.NET MAUI

.NET MAUI 10 enhances cross-platform app development. Notable features include multi-file selection, image compression, and WebView interception. Support for the latest Android APIs ensures apps run reliably on modern devices. MAUI’s improvements make it practical to share code across iOS, Android, macOS, and Windows while keeping platform-specific optimizations.

C# 14: What’s new

C# 14 introduces features designed to reduce boilerplate, improve readability, and make code safer and more expressive. Below are the key changes, explained with examples.

1. Field-backed properties

You can now access the compiler-generated backing field directly using the field keyword. This allows you to add custom logic without declaring a private field.

For a detailed guide on using the field keyword, see Understanding the field keyword in C# 14.

Example:

public class Person
{
    public string Name
    {
        get { return field; }
        set
        {
            if (string.IsNullOrWhiteSpace(value))
                throw new ArgumentException("Name cannot be empty.");
            field = value;
        }
    }
}

This keeps properties concise while still enabling validation or side-effects.

2. nameof supports unbound generics

Previously, nameof required a concrete type. Now you can reference generic types without arguments:

public string GetTypeName() => nameof(List<>); // returns "List"

3. Span<T> implicit conversions

C# 14 allows implicit conversions between Span<T> and ReadOnlySpan<T>, making low-level memory manipulation safer and easier:

ReadOnlySpan<char> span = "Hello".AsSpan(); // implicit conversion works

4. Lambda parameter modifiers

You can now use ref, in, or out in lambda parameters without specifying types explicitly:

Func<int, int> increment = ref x => x + 1;

This is particularly useful in high-performance code that manipulates structs.

5. Partial instance constructors and events

Partial instance constructors complement existing partial methods, making it easier to organize class initialization across files. Partial events allow event declarations to be split and extended in multiple files.

6. Extension blocks

C# 14 introduces static and instance extension blocks, allowing multiple extension methods or properties grouped together. This improves discoverability and keeps related extensions organized.

7. Null-conditional assignment

The new ?.= operator simplifies null checks:

Person p = null;
p?.Name = "John"; // assigns only if p is not null

8. User-defined operators

You can now define compound assignment (+=, -=) and increment/decrement (++, --) operators for your types, offering more control over custom behavior in your classes.

Why upgrade to .NET 10

From my perspective, .NET 10 is an ideal point to upgrade. Its combination of runtime performance improvements, SDK refinements, and C# 14 features allows developers to write cleaner, more efficient, and maintainable code. Minimal APIs, Blazor optimizations, and MAUI enhancements also make building modern web and cross-platform apps more straightforward.

Migrating now means benefiting from LTS support, improved developer experience, and access to the latest features without waiting for future versions.

Final thoughts

.NET 10 continues Microsoft’s commitment to performance, consistency, and developer productivity. While the runtime and libraries handle heavy lifting behind the scenes, C# 14 empowers developers to write more expressive and concise code.

For anyone building new projects or considering an upgrade, .NET 10 is a strong, safe, and feature-rich choice that will remain supported for years.