Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3 #34948

sander1095 · 2025-03-11T21:51:48Z

Description

Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3

Page URL

https://learn.microsoft.com/en-us/aspnet/core/release-notes/aspnetcore-10.0?view=aspnetcore-9.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/release-notes/aspnetcore-10.0.md

Document ID

a7ad4b01-2333-32d8-b759-e044edfb9102

Platform Id

2f8fb8ab-5309-0a77-987a-c867c6517d2b

Article author

@Rick-Anderson

Metadata

ID: a7ad4b01-2333-32d8-b759-e044edfb9102
PlatformId: 2f8fb8ab-5309-0a77-987a-c867c6517d2b
Service: aspnet-core
Sub-service: release-notes

Related Issues

guardrex · 2025-03-12T12:13:00Z

[Blazor] Response streaming default and opt-out

Covered by the PR at #34894.

cc: @pavelsavara @campersau ... and the PR includes the latest description info from the PR, including the breaking change piece.

maraf · 2025-03-19T09:28:43Z

[Blazor] End-to-end fingerprinting of assets in standalone mode

Most of the .NET assets are fingerprinted since .NET 9, with three exceptions. These changes to the standalone application will fill the missing pieces.

During build/publish it will override placeholders in index.html with values computed during build. It will put a fingerprint into the blazor.webassembly.js script and generate an importmap for other scripts that the .NET consists of and we need to load them via script name.

This setup is specific for standalone mode. In Blazor Web these are already handled with <ImportMap /> component and @Assets collection.

index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>BlazorWasmFingerprintingE2E</title>
    <base href="/" />
    ....
+    <script type="importmap"></script>
</head>

<body>
    <div id="app">
        <svg class="loading-progress">
            <circle r="40%" cx="50%" cy="50%" />
            <circle r="40%" cx="50%" cy="50%" />
        </svg>
        <div class="loading-progress-text"></div>
    </div>

    <div id="blazor-error-ui">
        An unhandled error has occurred.
        <a href="." class="reload">Reload</a>
        <span class="dismiss">🗙</span>
    </div>
-    <script src="_framework/blazor.webassembly.js"></script>
+    <script src="_framework/blazor.webassembly#[.{fingerprint}].js"></script>
</body>

</html>

blazorwasm.csproj

<Project Sdk="Microsoft.NET.Sdk.BlazorWebAssembly">

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
+    <WriteImportMapToHtml>true</WriteImportMapToHtml>
  </PropertyGroup>
</Project>

... resolved by #35057.

danroth27 · 2025-03-20T02:17:23Z

Original post from @sander1095:

Setting the Description in a ProducesResponseTypeAttribute works correctly for Minimal API aspnetcore#60539
- I added a new Description property to ASP.NET Core's [ProducesResponseType] in preview 1, but the Description property didn't work well for Minimal API's. This has now been fixed. This might be worth mentioning, or not, if the team considers this a bug fix. However, I do think the ASP.NET Core team would want to promote setting Descriptions via Support registering OpenApiOperationTransformer via extension method for Minimal APIs aspnetcore#59180 instead for Minimal API's. I Personally believe that ProducesResponseType is still the best option for setting response descriptions for controllers.
  - I'm going to create a package with useful OpenAPI transformers so this can be done even easier. Let me know if the team thinks this would be docs-worthy when that's finished!
Add Microsoft.AspNetCore.OpenApi to the webapiaot template (with an optional flag to disable it) aspnetcore#60337
- When you run dotnet new webapiaot, the template will come with OpenAPI support out of the box. This can be disabled with --no-openapi.

Other bug fixes: dotnet/aspnetcore#60937

EDIT: @Rick-Anderson

guardrex · 2025-03-26T15:03:33Z

[Blazor] Rename `DisableMatchAllIgnoresLeftUriPart`

... to EnableMatchAllForQueryStringAndFragmentSwitchKey.

cc: @ilonatommy

... resolved by #35056.

guardrex · 2025-03-27T12:46:13Z

[Blazor] Fix use of ReconnectModal in Blazor templates

cc: @oroztocil ... I'll update the guidance for the changes that you mention.

... ~~tracked by #35070~~. No changes needed.

guardrex · 2025-03-27T12:57:06Z

[Blazor] Support for declaratively persisting component and services state

cc: @javiercn ... Document now (Pre3) or wait for the dust to settle on it in a future preview?

... resolved by #35198.

guardrex · 2025-03-27T14:50:14Z

[Blazor] Standalone Blazor WASM MSBuild property `WasmApplicationEnvironmentName` to set the environment

cc : @maraf

... resolved by #35057.

guardrex · 2025-03-28T23:46:27Z

EDIT:

Validation support in Minimal APIs

Support for validation in Minimal APIs is now available. This feature allows you to request validation of data
sent to your API endpoints. When validation is enabled, the ASP.NET Core runtime will perform any validations
defined on query, header, and route parameters, as well as on the request body.
Validations can be defined using attributes in the System.ComponentModel.DataAnnotations namespace.
Developers can customize the behavior of the validation system by:

creating custom ValidationAttribute implementations
implement the IValidatableObject interface for complex validation logic

When validation fails, the runtime will return a 400 Bad Request response with
details of the validation errors.

To enable built-in validation support for minimal APIs, call the AddValidation extension method to register
the required services into the service container for your application.

builder.Services.AddValidation();

The implementation automatically discovers types that are defined in minimal API handlers or as base types of types defined in minimal API handlers. Validation is then performed on these types by an endpoint filter that is added for each endpoint.

Validation can be disabled for specific endpoints by using the DisableValidation extension method.

app.MapPost("/products",
    ([EvenNumber(ErrorMessage = "Product ID must be even")] int productId, [Required] string name)
        => TypedResults.Ok(productId))
    .DisableValidation();

>>>>>>>>>> Content below is outdated. <<<<<<<<<<<<<

[Minimal APIs] Document validation support for minimal APIs

Moved here from Safia's issue at #35090 (same deal ... the original issue lacked metadata) ...

In .NET 10 Preivew 3, we're introducing support for minimal API validation support.

I've created a sample repo and some notes on the implementation to serve as source material here: https://github.com/captainsafia/minapi-validation-support.

One thing to note is that this feature has a user-facing component for developers who are building minimal APIs and a framework component for developers who are building frameworks or their own validation libraries.

I think our first priority is developers building APIs since that's where the biggest product gap it exists.

mikekistler · 2025-04-04T15:16:22Z

Add Microsoft.AspNetCore.OpenApi to the webapiaot template

Support for OpenAPI document generation with the Microsoft.AspNetCore.OpenApi packagte is now included by default in the webapiaot project template. This support can be disabled if desired by using the --no-openapi flag when creating a new project.

This was a community contribution by @sander1095. Thanks for this contribution!

Moved to WN as include, did an edit sweep. Resolved with PR WN .NET 10 Prev3: Add OpenAPI to webapiaot #35192 [wadepickett]

mikekistler · 2025-04-04T21:14:42Z

Support for Server-Sent Events (SSE)

ASP.NET Core now supports returning a ServerSentEvents result using the TypedResults.ServerSentEvents API.
This feature is supported in both Minimal APIs and controller-based apps.

Server-Sent Events (SSE) is a server push technology that allows a server to send a stream of event messages to a
client over a single HTTP connection. In .NET the event messages are represented as SseItem objects, which may contain an event type, an ID, and a data payload of type T.

The TypedResults class has a new static method called ServerSentEvents that can be used to return a ServerSentEvents result. The first parameter to this method is an IAsyncEnumerable<SseItem<T>> that represents the stream of event messages to be sent to the client.

The following example illustrates how to use the TypedResults.ServerSentEvents API to return a stream of heart rate events as JSON objects to the client:

app.MapGet("/json-item", (CancellationToken cancellationToken) =>
{
    async IAsyncEnumerable<HeartRateEvent> GetHeartRate(
        [EnumeratorCancellation] CancellationToken cancellationToken)
    {
        while (!cancellationToken.IsCancellationRequested)
        {
            var heartRate = Random.Shared.Next(60, 100);
            yield return HeartRateEvent.Create(heartRate);
            await Task.Delay(2000, cancellationToken);
        }
    }

    return TypedResults.ServerSentEvents(GetHeartRate(cancellationToken), eventType: "heartRate");
});

EDIT: @Rick-Anderson :

Document Server Sent Event result type support in minimal APIs #35089

wadepickett · 2025-04-09T16:20:13Z

@Rick-Anderson, I don't have any here for SignalR or gRPC, so I am just picking ones at random to edit and quickly pull in as an include. I'm doing Validation support in Minimal APIs at the moment, can you pull in Add Microsoft.AspNetCore.OpenApi to the webapiaot template or Support for Server-Sent Events (SSE)?

wadepickett · 2025-04-09T19:36:32Z

..moving to include and editing Add Microsoft.AspNetCore.OpenApi to the webapiaot template

wadepickett · 2025-04-10T22:29:41Z

@danroth27, @mikekistler, @danmoseley, @sander1095 and @cmastr: This What's New topic update for .NET 10 Preview 3 was published today just after the .NET 10 Prev 3 release notes link was made available on the SDK download page. Thanks everyone for the fantastic help!

dotnetrepoman bot added aspnet-core/svc release-notes/subsvc Source - Docs.ms Docs Customer feedback via GitHub Issue labels Mar 11, 2025

dotnet-policy-service bot added the ⌚ Not Triaged label Mar 11, 2025

Rick-Anderson added the 10.0 .NET 10 label Mar 12, 2025

guardrex removed the ⌚ Not Triaged label Mar 12, 2025

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guardrex mentioned this issue Mar 20, 2025

No guidance for CSP #34351

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This was referenced Mar 20, 2025

WN10: Description property added to [ProducesResponseType] & ProducesResponseType #35016

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Document useful OpenAPI transformers sander1095/AspNetCore.OpenApi.Transformer.Extensions#5

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guardrex mentioned this issue Mar 21, 2025

[Pre3] Fingerprinting in Blazor WebAssembly #35023

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This was referenced Mar 25, 2025

[Pre3] Response streaming default and opt-out #34894

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[Pre3] Rename DisableMatchAllIgnoresLeftUriPart #35056

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[Pre3] Blazor WASM fingerprinting and environment property #35057

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Document Server Sent Event result type support in minimal APIs #35089

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Prep only: WN: Validation Support Min API: Orig draft #35187

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WN .NET 10 Prev 3: Validation Support Minimal API #35188

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Prep only: WN .NET10 Prev 3: webapiaot template adds OpenAPI #35190

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WN .NET 10 Prev3: Add OpenAPI to webapiaot #35192

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Document validation support for minimal APIs #35090

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Blazor Pre3 final updates for release #35200

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Publish WN 10 Prev 3: Update aspnetcore-10.0.md #35202

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Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3 #34948

Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3 #34948

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edited by danroth27

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Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3 #34948

Update the "What's new in ASP.NET Core 10.0" for .NET 10 Preview 3 #34948

Comments

sander1095 commented Mar 11, 2025 • edited by danroth27 Loading

Description

Page URL

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Document ID

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Metadata

guardrex commented Mar 12, 2025

[Blazor] Response streaming default and opt-out

maraf commented Mar 19, 2025 • edited by guardrex Loading

[Blazor] End-to-end fingerprinting of assets in standalone mode

index.html

blazorwasm.csproj

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danroth27 commented Mar 20, 2025 • edited by Rick-Anderson Loading

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guardrex commented Mar 26, 2025 • edited Loading

[Blazor] Rename DisableMatchAllIgnoresLeftUriPart

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guardrex commented Mar 27, 2025 • edited Loading

[Blazor] Fix use of ReconnectModal in Blazor templates

guardrex commented Mar 27, 2025 • edited Loading

[Blazor] Support for declaratively persisting component and services state

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guardrex commented Mar 27, 2025 • edited Loading

[Blazor] Standalone Blazor WASM MSBuild property WasmApplicationEnvironmentName to set the environment

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guardrex commented Mar 28, 2025 • edited Loading

Validation support in Minimal APIs

>>>>>>>>>> Content below is outdated. <<<<<<<<<<<<<

[Minimal APIs] Document validation support for minimal APIs

mikekistler commented Apr 4, 2025 • edited by wadepickett Loading

Add Microsoft.AspNetCore.OpenApi to the webapiaot template

mikekistler commented Apr 4, 2025 • edited by Rick-Anderson Loading

Support for Server-Sent Events (SSE)

wadepickett commented Apr 9, 2025

wadepickett commented Apr 9, 2025

wadepickett commented Apr 10, 2025 • edited Loading

sander1095 commented Mar 11, 2025 •

edited by danroth27

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maraf commented Mar 19, 2025 •

edited by guardrex

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danroth27 commented Mar 20, 2025 •

edited by Rick-Anderson

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guardrex commented Mar 26, 2025 •

edited

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[Blazor] Rename `DisableMatchAllIgnoresLeftUriPart`

guardrex commented Mar 27, 2025 •

edited

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guardrex commented Mar 27, 2025 •

edited

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guardrex commented Mar 27, 2025 •

edited

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[Blazor] Standalone Blazor WASM MSBuild property `WasmApplicationEnvironmentName` to set the environment

guardrex commented Mar 28, 2025 •

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mikekistler commented Apr 4, 2025 •

edited by wadepickett

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mikekistler commented Apr 4, 2025 •

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