[Breaking change]: Change to default RID when targeting .NET Framework

[marcpopMSFT]

Description

In .NET 8, we introduced a change to use a smaller RID graph when targeting net8.0 and higher: https://learn.microsoft.com/en-us/dotnet/core/compatibility/sdk/8.0/rid-graph

However, this breaks customers who are multi-targeting between net8 and .NET Framework as the restore happens once but the Framework project tries to use the old RID default and the .NET Core project tries to use the new reduced RID-graph.

To enable this multi-targeting scenario, we switched to using a default RID in this scenario that is compatible with the new RID graph.

Version

.NET 9 GA

Previous behavior

.NET Framework targeted SDK-style projects with no RID set would default to win7-x86 or win7-x64.

New behavior

.NET Framework targeted SDK-style projects with no RID set would default to win-x86 or win-x64.

Type of breaking change

• Binary incompatible: Existing binaries might encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
• Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code might require source changes to compile successfully.
• Behavioral change: Existing binaries might behave differently at run time.

Reason for change

.NET Framework applications were getting a default RID incompatible with our portable RID graph and would get a restore error:
Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error NETSDK1047: Assets file 'D:\a\_work\1\s\artifacts\obj\MSBuild\project.assets.json' doesn't have a target for 'net472/win7-x64'. Ensure that restore has run and that you have included 'net472' in the TargetFrameworks for your project. You may also need to include 'win7-x64' in your project's RuntimeIdentifiers. [MSBuild.csproj::TargetFramework=net472]

dotnet/sdk#35575

Recommended action

Update your RuntimeIdentifier to a value supported by the portable RID graph or switch back to the old RID graph by setting UseRidGraph=true.

Feature area

SDK

Affected APIs

No response

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Associated WorkItem - 345577