C# Announcing .NET Framework 4.8 Early Access build 3673

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Namrata Karnam

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We are happy to share the next Early Access build for the .NET Framework 4.8. This includes an updated .NET 4.8 runtime as well as the .NET 4.8 Developer Pack (a single package that bundles the .NET Framework 4.8 runtime, the .NET 4.8 Targeting Pack and the .NET Framework 4.8 SDK).

Please help us ensure this is a high quality and compatible release by trying out this build and exploring the new features.

Next steps:
To explore the new features, download the .NET 4.8 Developer Pack build 3673. If you want to try just the .NET 4.8 runtime, you can download either of these:


Please provide your feedback by .NET Framework Early Access GitHub repository.

Please note: This release is still under development and you can expect to see more features and fixes in future preview builds. Also, a reminder that this build is not supported for production use.

This preview build 3673 includes a key improvement/fix in the WPF area:

        • [WPF] – High DPI Enhancements

You can see the complete list of improvements in this build here .

.NET Framework build 3673 is also included in the next update for Windows 10. You can sign up for Windows Insiders to validate that your applications work great on the latest .NET Framework included in the latest Windows 10 releases.

WPF – High DPI Enhancements


WPF has added support for Per-Monitor V2 DPI Awareness and Mixed-Mode DPI scaling in .NET 4.8. Additional information about these Windows concepts is available here.

The latest Developer Guide for Per monitor application development in WPF states that only pure-WPF applications are expected to work seamlessly in a high-DPI WPF application and that Hosted HWND’s and Windows Forms controls are not fully supported.

.NET 4.8 improves support for hosted HWND’s and Windows Forms interoperation in High-DPI WPF applications on platforms that support Mixed-Mode DPI scaling (Windows 10 v1803). When hosted HWND’s or Windows Forms controls are created as Mixed-Mode DPI scaled windows, (as described in the “Mixed-Mode DPI Scaling and DPI-aware APIs” documentation by calling SetThreadDpiHostingBehavior and SetThreadDpiAwarenessContext API’s), it will be possible to host such content in a Per-Monitor V2 WPF application and have them be sized and scaled appropriately. Such hosted content will not be rendered at the native DPI – instead, the OS will scale the hosted content to the appropriate size.

The support for Per-Monitor v2 DPI awareness mode also allows WPF controls to be hosted (i.e., parented) under a native window in a high-DPI application. Per-Monitor V2 DPI Awareness support will be available on Windows 10 v1607 (Anniversary Update). Windows adds support for child-HWND’s to receive DPI change notifications when Per-Monitor V2 DPI Awareness mode is enabled via the application manifest.

This support is leveraged by WPF to ensure that controls that are hosted under a native window can respond to DPI changes and update themselves. For e.g.- a WPF control hosted in a Windows Forms or a Win32 application that is manifested as Per Monitor V2 – will now be able to respond correctly to DPI changes and update itself.

Note that Windows supports Mixed-Mode DPI scaling on Windows 10 v1803, whereas Per-Monitor V2 is supported on v1607 onwards.

To try out these features, the following application manifest and AppContext flags must be enabled:

1. Enable Per-Monitor DPI in your application

  • Turn on Per-Monitor V2 in your app.manifest

2. Turn on High DPI support in WPF

  • Target .NET Framework 4.6.2 or greater

and

3. Set AppContext switch in your app.config


Alternatively,

Set AppContextSwitch Switch.System.Windows.DoNotUsePresentationDpiCapabilityTier2OrGreater=false in App.Config to enable Per-Monitor V2 and Mixed-Mode DPI support introduced in .NET 4.8.

The runtime section in the final App.Config might look like this:


AppContext switches can also be set in registry. You can refer to the AppContext Class for additional documentation.

Closing
We will continue sharing early builds of the next release of the .NET Framework via the Early Access Program on a regular basis for your feedback. As a member of the .NET Framework Early Access community you play a key role in helping us build new and improved .NET Framework products. We will do our best to ensure these early access builds are stable and compatible, but you may see bugs or issues from time to time. It would help us greatly if you would take the time to report these to us on Github so we can address these issues before the official release.

Thank you!

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