What’s New in .NET 10 – Performance, C# 14, Blazor & ASP.NET Core Improvements

Microsoft officially released .NET 10 on November 11, 2025, and it marks one of the most significant upgrades in the .NET ecosystem. As a Long-Term Support (LTS) release, it will get updates and security patches until November 2028, giving developers long-term stability for web apps, APIs, cloud workloads, mobile apps, and enterprise systems.

In this first part of the series, we cover the biggest improvements in:

• JIT and runtime performance

• C# 14

• Blazor

• ASP.NET Core 10

Massive Performance Gains with JIT Compiler Improvements

.NET 10 brings deep, behind-the-scenes optimizations through an enhanced Just-In-Time (JIT) compiler, delivering faster performance without changing your code.

1. Smarter Struct Handling

Earlier, struct members were written to memory before they were loaded into CPU registers.
.NET 10 now passes struct members directly into CPU registers, reducing unnecessary memory operations.

Benefit:
Faster method execution and lower overhead in struct-heavy applications.

2. Faster Array Iteration

When iterating arrays using IEnumerable, .NET 10 now removes virtual method calls and generates optimized machine code instead.

Great for:

• Data processing apps

• High-frequency loops

• Real-time APIs

3. Graph-Based Loop Inversion

A new algorithm enhances overall loop optimisation and improves hot-path performance.

Real-World Performance Benchmarks

• JSON serialization: ↑ 10% faster

• JSON deserialization: ↑ 8% faster

• Common API responses: ↑ up to 53% faster

These improvements directly improve app responsiveness and user experience.

C# 14: Cleaner, More Expressive & Less Boilerplate

C# 14 introduces multiple features that reduce ceremony and make your code easier to maintain.

1. Extension Members (A Major Addition)

A new extension block syntax groups all extension members for a type in one place.
You can now add:

• Extension properties

• Static extension methods

• Static extension properties

• User-defined operators

Example:

public static class Enumerable
{
    extension<TSource>(IEnumerable<TSource> source)
    {
        // Extension property
        public bool IsEmpty => !source.Any();

        // Extension method
        public IEnumerable<TSource> Where(Func<TSource, bool> predicate) { ... }
    }

    // Static extension members
    extension<TSource>(IEnumerable<TSource>)
    {
        public static IEnumerable<TSource> Combine(IEnumerable<TSource> first, 
                                                     IEnumerable<TSource> second) { ... }
    }
}

2. Null-Conditional Assignment

A new shorthand for setting properties only when the object isn’t null:
customer?.Order = GetCurrentOrder();


3. field Keyword for Backing Fields

Auto-implemented properties can now reference their own backing fields without writing boilerplate code.

4. Partial Instance Constructors & Partial Events

These additions enhance modular and maintainable class design.

Blazor Gets Major Speed & UX Upgrades

Blazor continues maturing as Microsoft’s full-stack web UI framework.

1. WebAssembly File Size Reduced by 76%

The core blazor.web.js file is now fingerprinted and compressed:

• Old size: 183 KB

• New size: ~43 KB

Result: Faster page loads, especially on mobile.

2. WebAssembly Rendering is 20% Faster

Startup time and runtime performance have been significantly improved.

3. Better Navigation Handling

NavigationManager.NavigateTo no longer jumps to the top during same-page navigations.

4. Better Reconnection Management

The new ReconnectModal component improves UX when WebSockets disconnect.

5. Form Validation Enhancements

Support now includes:

• Nested forms

• Collection validation

• [ValidatableType] attribute

• AddValidation() extension

6. Improved Authentication

Blazor now supports passkeys, enabling seamless passwordless authentication.

ASP.NET Core 10: Cleaner APIs, Better Validation & Smarter Documentation

ASP.NET Core 10 focuses on reducing boilerplate and improving the API developer experience.

1. Built-in Minimal API Validation

You can now use DataAnnotations directly on parameters:

app.MapPost("/products",
    ([Range(1, int.MaxValue)] int productId, [Required] string name) =>
        TypedResults.Ok(new { productId, name })
);

Validation is automatic, and you can disable it when needed.

2. OpenAPI 3.1 Support

You can add descriptive metadata using.WithOpenApi():

app.MapPost("/products", (Product product) =>
    Results.Created($"/products/{product.Id}", product))
    .WithOpenApi(op => {
        op.Summary = "Create a new product";
        op.Description = "Adds a product with name and price.";
        return op;
    });

3. Built-In Server-Sent Events (SSE)

Streaming real-time updates becomes easier without WebSockets.

4. Enhanced Diagnostics

You get improved tracing, authentication metrics, and better Blazor Server diagnostics.