.NET 10 Preview 7

[jongalloway]

.NET 10 Preview 7 is now available!

Today, we are excited to announce the seventh preview release of .NET 10 with enhancements across the .NET Runtime, SDK, libraries, C#, ASP.NET Core, Blazor, .NET MAUI, and more.

📥 Download .NET 10 Preview 7

What's New

📚 Libraries

• Launch Windows processes in new process group
• AES KeyWrap with Padding (IETF RFC 5649)
• ML-DSA
• Composite ML-DSA
• PipeReader support for JSON serializer
• WebSocketStream
• TLS 1.3 for macOS (client)

🛠️ SDK

• Use the any RuntimeIdentifier with platform-specific .NET Tools

🌐 ASP.NET Core & Blazor

• Configure suppressing exception handler diagnostics
• Avoid cookie login redirects for known API endpoints
• Passkey authentication improvements
• Support for the .localhost top-level domain
• Use PipeReader support in System.Text.Json
• Enhanced validation for classes and records
• Blazor improvements
• OpenAPI.NET dependency upgraded to stable release

📱 .NET MAUI

• XAML Source Generator
• MediaPicker EXIF Support
• SafeArea Enhancements
• Secondary Toolbar Items
• New Control APIs
• Deprecated API Removals

🖥️ Windows Forms

• ComboBox Dark Mode Rendering Fix
• RichTextBox Dark Mode Improvement and Known Limitation
• PropertyGrid Dark Mode Enhancements

🖥️ Windows Presentation Foundation (WPF)

• Bug Fixes
• Fluent Theme Improvements

🎁 Entity Framework Core

• Improved translation for parameterized collection
• Small improvements and bug fixes

📦 Container Images

• dnx is now on the PATH in SDK images

Release Notes

• Libraries
• Runtime
• SDK
• C#
• F#
• Visual Basic
• ASP.NET Core & Blazor
• .NET MAUI
• Windows Forms
• WPF
• Entity Framework Core
• Container Images

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Your feedback is important to us! Please share your thoughts and experiences with this preview release.

[MartinJohns]

Dear @jongalloway, you're giving us mixed signals here.

[jongalloway]

We love all our previews, we can't pick a favorite! Thanks, fixed. :)

[rod-mac]

I hope Dan Roth gets to read this as I have a major challenge with developing in Blazor moving forwards and I hope you can address.

I'm a drinks professional first, coder (definitely) second. A long time ago I wrote some apps in .NET framework (about 100,000 lines in webforms, winforms and SQL Server). Thanks to people like Johnny Papa, I got suggestions on how to make data requests execute extremely quickly at scale.

However, on the front and middle tiers, everything I've done needs a re-write, pretty much from scratch.

The appeal of Blazor running server side, browser client side and desktop is compelling. However, I've been putting off and putting off jumping into Blazor, concerns remaining that SignalR is going to fall over on a shared server with a lot of concurrent users whilst WASM will face the same security problems XBAPs had.

So, I thought it prudent to write a Blazor desktop and Blazor server app, with a Razor Pages project using AJAX calls as a fallback, this sharing and exchanging data with the Blazor apps.

However, I've run into the problem that myriad Blazor releases (template and API changes) are an issue because: CoPilot, including GTP-5 on GitHub, which starts off convincingly but quickly gets confused as it can't locate the correct template code for .NET 9 or 10, so it can't produce a simple, wotking solution which includes code, folder and file structure as a starting point; reference book sources are understandably considerably behind releases, e.g. Jimmy Engstrom's excellent Web Development With Blazor (.NET 8).

I'm hoping you can pick up on this 'template / getting started challenge' ahead of .NET 10's release in something like the e-book 'Blazor-for-ASP-NET-Web-Forms-Developers' (also excellent but also last updated for .NET 8). There's also a useful e-Commere project 'eShopOnWeb' out there (one with ski-ing gear), but it has the complexity of trying to master a second difficult thing i.e. Aspire. I'm thinking back to an old .NET framework demo app (was it I-buy-spy?) which was a super useful starter resource.

Thank you.

[rod-mac]

Just to add a small addendum to my last post, when .NET 1.0 (framework) came out, it felt like a complete solution, where controls, a design surface and state persistence were fleshed out ahead of launch. With .NET 10, 'out of the box' state persistence is just coming out. This in turn enabled Homer and Sussman et al to write a Wrox publication ASP.NET as a complete reference. We haven't got that kind of support today for the reasons I mentioned.

[rod-mac]

Just to add an update 2nd Sep on 3rd or 4th attempt with GPT-5 ad .NET 10 preview 7: finally got things right, though it took a few hours to fathom. Initial template code offering was good, but it then seemed to 'lose the place', coming up with examples using different namespaces, files and folder structures. I paused, left the chat open overnight and it seemed to get going OK again, though it definitely wasn't 5 minutes - now have Blazor and Razor Pages example sharing Razor Pages/AJAX calls - phew. So...

1. seems GPT-5 is beginning to fathom project/template code albeit folder structure and filenames seem to wobble at times;
2. I would kindly ask MS to refresh documentation and code samples ahead of .NET 10 launch e.g. 'IBuySpy' or 'eShopOnWeb' without and with Aspire, and an ePub refresh for 'Blazor-for-ASP-NET-Web-Forms-Developers' (maybe the ePub could work with the sample?).

Thank you MS for listening!

[yannic-hamann-abb]

How to handle message reads without throwing JsonException when the client gracefully disconnects?
I think an approach would be to pass a cancellation token to DeserializeAsync to get a better OperationCanceledException exception, but where would I get that token from?

Maybe there is a better approach to prevent the JsonSerializer from throwing, let me know. This use case will be very common.

using var webSocket = await ctx.WebSockets.AcceptWebSocketAsync();
using WebSocketStream webSocketStream = WebSocketStream.Create(webSocket, WebSocketMessageType.Text, true);

while (webSocketStream.CanRead)
{
   using WebSocketStream messageStream = WebSocketStream.CreateReadableMessageStream(webSocket);
    var appMessage = await JsonSerializer.DeserializeAsync<Message>(messageStream);
   // ...
}

[walid-khalafi]

You can avoid the JsonException on client disconnect by passing a CancellationToken to DeserializeAsync and triggering it when the WebSocket closes. This way, a normal disconnect results in an OperationCanceledException instead of being treated as malformed JSON.
Here’s an example:

using var webSocket = await ctx.WebSockets.AcceptWebSocketAsync();
using var webSocketStream = WebSocketStream.Create(webSocket, WebSocketMessageType.Text);
using var cts = new CancellationTokenSource();

while (webSocketStream.CanRead)
{
    using var messageStream = WebSocketStream.CreateReadableMessageStream(webSocketStream);
    try
    {
        var message = await JsonSerializer.DeserializeAsync<Message>(
            messageStream,
            cancellationToken: cts.Token
        );
    }
    catch (OperationCanceledException)
    {
        // Connection closed gracefully
        break;
    }
    catch (JsonException ex)
    {
        // Handle malformed JSON
        Console.WriteLine($"Invalid JSON: {ex.Message}");
    }
}

This pattern cleanly separates a normal disconnect from actual JSON parsing errors, and still lets you handle malformed payloads when needed.
Let me know if you’d like me to share a minimal repro or integrate this into your existing loop.

[yannic-hamann-abb]

Hi, thanks for sharing your thoughts. I can't run your example right now. But from what I see your provided code would still fail in every scenario with a JsonException, as the cts never cancels the token, or am I missing something? Also, from what I understand there is no easy way to hook into the client disconnected event to trigger the token. As the close event is read from the same stream.