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* .NET 10 Preview 6 * .NET 10 P6 - FSharp (#9946) * Update fsharp preview6 release notes with manual changes. * udpate for release * .NET 10 P6 - CSharp (#9943) * Add period to last sentence in csharp preview6 release notes. * update C# * .NET 10 P6 - EFCore (#9945) * Add period to last sentence in efcore preview6 release notes. * EF 10.0-preview.6 release notes * Added small improvements --------- Co-authored-by: Shay Rojansky <roji@roji.org> * .NET 10 P6 - WPF (#9952) * Add period to last sentence in aspnetcore preview6 release notes. * Add period to last sentence in containers preview6 release notes. * Add period to last sentence in csharp preview6 release notes. * Add period to last sentence in dotnetmaui preview6 release notes. * Add period to last sentence in efcore preview6 release notes. * Add period to last sentence in libraries preview6 release notes. * Add period to last sentence in runtime preview6 release notes. * Add period to last sentence in sdk preview6 release notes. * Add period to last sentence in visualbasic preview6 release notes. * Add period to last sentence in winforms preview6 release notes. * Add period to last sentence in wpf preview6 release notes. * Revert all changes except wpf.md in dotnet10-p6-wpf branch. * Add WPF info * update feature list --------- Co-authored-by: Andy (Steve) De George <67293991+adegeo@users.noreply.github.com> * .NET 10 P6 - WinForms (#9951) * Add period to last sentence in winforms preview6 release notes. * Update WinForms for Preview 6 * Apply suggestions from code review Co-authored-by: Klaus Löffelmann <9663150+KlausLoeffelmann@users.noreply.github.com> --------- Co-authored-by: Merrie McGaw <mmcgaw@microsoft.com> Co-authored-by: Klaus Löffelmann <9663150+KlausLoeffelmann@users.noreply.github.com> * .NET 10 P6 - SDK (#9949) * Add period to last sentence in sdk preview6 release notes. * CLI notes around tools and such * Add release notes for preview.6 run-file changes --------- Co-authored-by: Chet Husk <baronfel@users.noreply.github.com> Co-authored-by: Damian Edwards <damian@damianedwards.com> * .NET 10 P6 - Containers (#9942) * Add period to last sentence in containers preview6 release notes. * update to none udpates. * .NET 10 P6 - Runtime (#9948) * Add period to last sentence in runtime preview6 release notes. * Add JIT notes --------- Co-authored-by: Aman Khalid (from Dev Box) <amankhalid@microsoft.com> * .NET 10 P6 - .NET MAUI (#9944) * Add period to last sentence in dotnetmaui preview6 release notes. * Update dotnetmaui.md * adding more details for android * minor updates to iOS note * Update release-notes/10.0/preview/preview6/dotnetmaui.md Co-authored-by: Jonathan Peppers <jonathan.peppers@microsoft.com> * Update release-notes/10.0/preview/preview6/dotnetmaui.md Co-authored-by: Jonathan Peppers <jonathan.peppers@microsoft.com> * Update release-notes/10.0/preview/preview6/dotnetmaui.md Co-authored-by: Jonathan Peppers <jonathan.peppers@microsoft.com> * added contributors from android and iOS repos --------- Co-authored-by: David Ortinau <david.ortinau@microsoft.com> Co-authored-by: Jonathan Peppers <jonathan.peppers@microsoft.com> * .NET 10 P6 - Libraries (#9947) * Add period to last sentence in libraries preview6 release notes. * Update libraries.md * Update libraries.md Co-authored-by: Weihan Li <weihanli@outlook.com> * Update libraries.md fix link --------- Co-authored-by: Pranav Senthilnathan <pranas@microsoft.com> Co-authored-by: Weihan Li <weihanli@outlook.com> * Add ASP.NET Core release notes for .NET 10 Preview 6 (#9965) * update linter * revert * Fix link to installers and binaries for .NET 10 Preview 6 in README.md * update permissions? * Update release notes for .NET 10 Preview 6: enhance dark mode support in Windows Forms, improve JSON property handling in libraries, and refine CLI tool execution options in SDK. * Enhance release notes for .NET 10 Preview 6: update dark mode support in Windows Forms, improve formatting in EF Core and SDK documentation, and clean up whitespace in various markdown files. * cleanup * add p6 * lint * try this * Update releases.md * Update README.md * Update release-notes/README.md * Update releases-index.json * Update install-linux.md * Update install-macos.md * Update install-windows.md * Update releases.json * Update 10.0.0-preview.6.md * Added release.json * Mix lint errors in release.json for preview 6 release * Fix jsonlint errors * Fix jsonlint errors --------- Co-authored-by: Shay Rojansky <roji@roji.org> Co-authored-by: Andy (Steve) De George <67293991+adegeo@users.noreply.github.com> Co-authored-by: Merrie McGaw <mmcgaw@microsoft.com> Co-authored-by: Klaus Löffelmann <9663150+KlausLoeffelmann@users.noreply.github.com> Co-authored-by: Chet Husk <baronfel@users.noreply.github.com> Co-authored-by: Damian Edwards <damian@damianedwards.com> Co-authored-by: Aman Khalid (from Dev Box) <amankhalid@microsoft.com> Co-authored-by: David Ortinau <david.ortinau@microsoft.com> Co-authored-by: Jonathan Peppers <jonathan.peppers@microsoft.com> Co-authored-by: Pranav Senthilnathan <pranas@microsoft.com> Co-authored-by: Weihan Li <weihanli@outlook.com> Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com> Co-authored-by: victorisr <victorisr@microsoft.com> Co-authored-by: Jon Galloway <jongalloway@gmail.com>
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ASP.NET Core in .NET 10 Preview 6 - Release Notes
Here's a summary of what's new in ASP.NET Core in this preview release:
- Automatic eviction from memory pool
- Blazor WebAssembly preloading
- Blazor build producing javascript bundler friendly output
- Improved form validation for Blazor
NavigationManager.NotFound()works after streaming has started- Blazor diagnostics improvements
- Blazor Server state persistence
- Disabling
NavigationExceptionusage is now opt-in - Add passkey support to ASP.NET Core Identity
- Minimal API validation integration with
IProblemDetailsService - Validation APIs moved to extensions package
ASP.NET Core updates in .NET 10:
- What's new in ASP.NET Core in .NET 10 documentation.
- Breaking changes
- Roadmap
Automatic eviction from memory pool
Memory pools used by Kestrel, IIS, and HTTP.sys now release unused memory when applications are idle, improving resource efficiency.
Why it matters: Previously, pooled memory stayed reserved even when unused. Now memory is automatically returned to the system during idle periods, reducing overall memory usage.
How to use: No action needed. This works automatically.
There are also metrics available for the memory pool under the name Microsoft.AspNetCore.MemoryPool. See the ASP.NET Core metrics documentation for more information.
You can create custom memory pools using the new IMemoryPoolFactory service interface:
public class MyBackgroundService : BackgroundService
{
private readonly MemoryPool<byte> _memoryPool;
public MyBackgroundService(IMemoryPoolFactory<byte> factory)
{
_memoryPool = factory.Create();
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
try
{
await Task.Delay(20, stoppingToken);
// do work that needs memory
var rented = _memoryPool.Rent(100);
rented.Dispose();
}
catch (OperationCanceledException)
{
return;
}
}
}
}
To replace the default memory pool with a custom implementation:
services.AddSingleton<IMemoryPoolFactory<byte>, CustomMemoryPoolFactory>();
public class CustomMemoryPoolFactory : IMemoryPoolFactory<byte>
{
public MemoryPool<byte> Create()
{
return MemoryPool<byte>.Shared; // or custom implementation
}
}
Blazor WebAssembly preloading
Blazor now provides a <LinkPreload /> component that generates link tags for preloading framework assets instead of using link headers. This gives better control over preloading behavior and correctly identifies the application's base URL.
To enable preloading, add the <LinkPreload /> component to your application's head:
<head>
<base href="/" />
+ <LinkPreload />
...
</head>
Remove the component to disable preloading, which is useful when using the loadBootResource callback to modify URLs.
Blazor build producing javascript bundler friendly output
Make Blazor WebAssembly compatible with JavaScript bundlers like webpack or rollup by setting the WasmBundlerFriendlyBootConfig property to true.
<PropertyGroup>
<WasmBundlerFriendlyBootConfig>true</WasmBundlerFriendlyBootConfig>
</PropertyGroup>
This adjusts the boot configuration to use import statements for framework assets that JavaScript bundlers can then use to correctly identify related files. The build output won't be directly runnable in the browser; post processing by JavaScript tools is expected.
Improved form validation for Blazor
Blazor now supports validating nested objects and collection items in forms.
To use this feature:
- Call
AddValidation()in your application setup - Create model types in .cs files (not .razor files)
- Add the
[ValidatableType]attribute to your root model type
Without these steps, validation works the same as before (top-level only).
Note: The [ValidatableType] attribute is experimental and causes a build error. Suppress the diagnostic to use this feature.
Example:
// Program.cs
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddRazorComponents();
builder.Services.AddValidation(); // Enable new validation behavior
// Data/OrderModel.cs
#pragma warning disable ASP0029 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
[ValidatableType]
#pragma warning restore ASP0029 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
public class OrderModel
{
public CustomerModel CustomerDetails { get; set; } = new CustomerModel();
public List<OrderItemModel> OrderItems { get; set; } = new List<OrderItemModel>();
}
public class CustomerModel
{
[Required(ErrorMessage = "Name is required.")]
public string? FullName { get; set; }
[Required(ErrorMessage = "Email is required.")]
[EmailAddress(ErrorMessage = "Invalid email address.")]
public string? Email { get; set; }
public AddressModel ShippingAddress { get; set; } = new AddressModel();
}
@* Pages/Order.razor *@
<EditForm Model="@order">
<DataAnnotationsValidator />
<h4>Customer Details</h4>
<div class="mb-3">
<label for="customerFullName">Full Name</label>
<InputText id="customerFullName" @bind-Value="order.CustomerDetails.FullName" />
<ValidationMessage For="@(() => order.CustomerDetails.FullName)" />
</div>
<!-- Additional form fields -->
</EditForm>
@code {
private OrderModel order = new OrderModel();
}
Model types must be in .cs files because validation uses source generators, and one source generator's output can't be input for another.
NavigationManager.NotFound() works after streaming has started
NavigationManager.NotFound() now works even after response streaming begins, enabling better error handling when content has already started streaming but a not found condition occurs later.
Blazor diagnostics improvements
Blazor Server traces are now top-level activities instead of being nested under HTTP or SignalR activities. This simplifies viewing traces in diagnostic tools like the .NET Aspire dashboard or Application Insights.
The CircuitStart trace moved to a separate Microsoft.AspNetCore.Components.Server.Circuits source.
To configure the new trace source:
builder.Services.ConfigureOpenTelemetryTracerProvider(tracerProvider =>
{
tracerProvider.AddSource("Microsoft.AspNetCore.Components");
+ tracerProvider.AddSource("Microsoft.AspNetCore.Components.Server.Circuits");
});
Blazor Server state persistence
Blazor Server apps now persist declared circuit state before evicting circuits from memory. When clients reconnect after extended periods, apps can restore circuit state, letting users resume their work uninterrupted.
Why it matters: Previously, circuit eviction meant losing all client state. Users had to restart, losing progress and creating poor experiences. State persistence maintains continuity even when circuits are temporarily removed from memory.
How it works:
Circuit state persists in memory or using HybridCache if configured. Only declared state is persisted.
You can implement custom policies using the new Blazor.pause() and Blazor.resume() JavaScript APIs. These control when circuits pause and resume based on your needs. For example, pause when idle, during server restarts, or when browser tabs aren't visible. Paused circuits persist to the client, freeing server resources.
Example - pause the app when hidden and resume when visible to save server resources:
// Pause when tab becomes hidden, resume when visible
document.addEventListener('visibilitychange', () => {
if (document.hidden) {
Blazor.pause();
} else {
Blazor.resume();
}
});
Disabling NavigationException usage is now opt-in
To improve backwards compatibility, disabling NavigationException for Blazor page navigations is now opt-in. The configuration switch was renamed with an updated default value:
- "Microsoft.AspNetCore.Components.Endpoints.NavigationManager.EnableThrowNavigationException", default value: false
+ "Microsoft.AspNetCore.Components.Endpoints.NavigationManager.DisableThrowNavigationException", default value: true
The Blazor Web App template disables NavigationException usage for more consistent navigation behavior across render modes.
Add passkey support to ASP.NET Core Identity
ASP.NET Core Identity now supports passkey authentication based on WebAuthn and FIDO2 standards. Passkeys provide a modern, phishing-resistant authentication method using public key cryptography and device-based authentication, allowing users to sign in without passwords using biometrics or security keys.
The Blazor Web App template includes built-in passkey management and login functionality.
Developers can use new APIs to add passkey authentication to existing applications.
Minimal API validation integration with IProblemDetailsService
Minimal API validation error responses can now be customized using an IProblemDetailsService implementation in the services collection (DI container). This enables more consistent and user-specific error responses.
Community contribution from @marcominerva. Thank you!
Validation APIs moved to extensions package
The validation APIs moved to the Microsoft.Extensions.Validation namespace and NuGet package, making them usable outside ASP.NET Core scenarios. The public APIs and behavior remain the same, just under a new package and namespace. Existing projects should work without code changes as old references redirect to the new implementation. The APIs are marked as experimental and subject to future changes.
Contributors
Thank you contributors! ❤️