We're excited to announce our first release candidate for .NET 9!

Note: these are the base SDKs that add support for the platforms in question. For MAUI (which is built on top of our SDKs), visit: https://learn.microsoft.com/dotnet/maui/.

This release consists of the following versions:

• iOS: 17.5.9270-net9-rc1
• tvOS: 17.5.9270-net9-rc1
• Mac Catalyst: 17.5.9270-net9-rc1
• macOS: 14.5.9270-net9-rc1

🚨 This release requires Xcode 15.4

Full release notes: .NET 9 release notes
Known issues: Known issues in .NET 9

What's Changed

• [main] Update dependencies from dotnet/xharness by @dotnet-maestro in #20902
• Reenable dedup optimization for all AOT modes by @ivanpovazan in #20936
• Do not enable dedup when targeting maccatalyst-x64 by @ivanpovazan in #20945
• [net9.0] Update dependencies from dotnet/sdk by @dotnet-maestro in #20948
• [ci] Update post-build pipeline triggers by @pjcollins in #20950
• [main] Enable dedup only when targeting arm64 by @dalexsoto in #20953
• [net9.0] Merge main into net9.0 by @dalexsoto in #20956
• Bump maccore. by @rolfbjarne in #20960
• [main] Update dependencies from dotnet/xharness by @dotnet-maestro in #20927
• Add Xcsync tool to workload package by @mcumming in #20931
• [net9.0] Update dependencies from dotnet/sdk by @dotnet-maestro in #20949
• Fail the build if global.json was updated. by @rolfbjarne in #20983
• [net9.0] [xcsync] Add xcsync to the SignList.xml by @dalexsoto in #20978
• [net9.0] [xcsync] Rename xcsync script to dotnet-xcsync by @mcumming in #20986
• [xtro] Enable Mac Catalyst. by @rolfbjarne in #20974
• [net9.0] Merge main into net9.0. by @rolfbjarne in #20973
• [net9.0] [xcsync] Bump xcsync to 1.0.90 by @mcumming in #20987
• [net9.0] [dotnet] Delay computing trimming options until MAUI has had a chance to change the default. by @rolfbjarne in #20971
• [dotnet] Delay computing trimming options until MAUI has had a chance to change the default. by @rolfbjarne in #20970
• [net9.0] [xcsync] Add open argument to generate target by @mcumming in #20979
• [maestro] Rearrange lines to try to have fewer merge conflicts. by @rolfbjarne in #20984
• [net9.0] [xcsync] Fix unix file permissions for xcsync by @mcumming in #20997
• [net9.0] Merge main into net9.0. by @rolfbjarne in #20996
• [main] Update dependencies from dotnet/installer by @dotnet-maestro in #20932
• [ObjCRuntime] Allow a null delegate in Runtime.ReleaseBlockWhenDelegateIsCollected. Fixes #20920. by @rolfbjarne in #20999
• [devops] Publish Xcode 16 builds. by @rolfbjarne in #21006
• [github] Add a much better issue template. by @rolfbjarne in #21007
• [github] Fix issue template syntax. by @rolfbjarne in #21014
• [net9.0] Update dependencies from dotnet/sdk by @dotnet-maestro in #20994
• [src/runtime] Add extra checks to Runtime.IsUserType to detect invalid pointers. by @rolfbjarne in #21001
• [tests] Improve the CustomizedCodeSigning tests to not depend on file order. by @rolfbjarne in #20889
• [ci] Simplify shipping drop metadata names by @pjcollins in #21003
• [main] Update dependencies from dotnet/xharness by @dotnet-maestro in #21017
• [net9.0] Update dependencies from dotnet/sdk by @dotnet-maestro in #21022
• [bgen] Add support for NSNumber as the underlying type for Objective-C fields. by @rolfbjarne in #21018
• [devops] Publish Xcode 16 builds (take 2). by @rolfbjarne in #21025
• [net9.0] Update dependencies from dotnet/sdk by @dotnet-maestro in #21031
• [net9.0] Merge main into net9.0. by @rolfbjarne in #21038
• [ci] Support stable publishing and passwordless auth for darc/maestro by @pjcollins in #20914
• Don't encode underscore in AOT symbol name by @akoeplinger in #21069
• [release/9.0.1xx-rc1] [dotnet] Make the RelativeMlaunchPath and XamarinRelativeSdkRootDirectory properties public. by @vs-mobiletools-engineering-service2 in #21079
• [release/9.0.1xx-rc1] [build] Make package metadata optional by @vs-mobiletools-engineering-service2 in #21109
• [release/9.0.1xx-rc1] [net9.0] Bump the .NET 8 / Xcode 15.4 bits to latest stable. by @vs-mobiletools-engineering-service2 in #21103
• [release/9.0.1xx-rc1] Fix calculating the branch name if BRANCH_NAME isn't set. by @vs-mobiletools-engineering-service2 in #21125
• [release/9.0.1xx-rc1] [net9.0] Bump .NET Xcode 15.4 packages to latest by @vs-mobiletools-engineering-service2 in #21133
• [release/9.0.1xx-rc1] Remove xcsync from SDK and install as .NET Global Tool by @mcumming in #21127

Full Changelog: dotnet-9.0.1xx-preview7-9231...dotnet-9.0.1xx-rc1-9270