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OSPlatform attributes renamed or removed

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The following attributes that were introduced in .NET 5 Preview 8 have been removed or renamed: MinimumOSPlatformAttribute, RemovedInOSPlatformAttribute, and ObsoletedInOSPlatformAttribute.

Change description

.NET 5 Preview 8 introduced the following attributes in the System.Runtime.Versioning namespace:

  • MinimumOSPlatformAttribute
  • RemovedInOSPlatformAttribute
  • ObsoletedInOSPlatformAttribute

In .NET 5 Preview 8, when a project targets an OS-specific flavor of .NET 5 by using a target framework moniker such as net5.0-windows, the build adds an assembly-level System.Runtime.Versioning.MinimumOSPlatformAttribute attribute.

In .NET 5 RC1, the ObsoletedInOSPlatformAttribute has been removed, and MinimumOSPlatformAttribute and RemovedInOSPlatformAttribute have been renamed as follows:

Preview 8 name RC1 and later name
MinimumOSPlatformAttribute SupportedOSPlatformAttribute
RemovedInOSPlatformAttribute UnsupportedOSPlatformAttribute

In .NET 5 RC1 and later, when a project targets an OS-specific flavor of .NET 5 by using a target framework moniker such as net5.0-windows, the build adds an assembly-level SupportedOSPlatformAttribute attribute.

Reason for change

.NET 5 Preview 8 introduced attributes in System.Runtime.Versioning to specify supported platforms for APIs. The attributes are consumed by the Platform compatibility analyzer to produce build warnings when platform-specific APIs are consumed on platforms that don't support those APIs.

For .NET 5 RC1, an additional feature was added to the platform compatibility analyzer for platform exclusion. The feature allows APIs to be marked as entirely unsupported on OS platforms. That feature prompted changes to the attributes, including using more suitable names. The ObsoletedInOSPlatformAttribute was removed because it was no longer needed.

Version introduced

5.0 RC1

When you retarget your project from .NET 5 Preview 8 to .NET 5 RC1, you might encounter build or run-time errors due to these changes. For example, the renaming of MinimumOSPlatformAttribute is likely to produce errors, because the attribute is applied to platform-specific assemblies at build time, and old build artifacts will still reference the old API name.

Example build-time errors:

  • error CS0246: The type or namespace name 'MinimumOSPlatformAttribute' could not be found (are you missing a using directive or an assembly reference?)
  • error CS0246: The type or namespace name 'RemovedInOSPlatformAttribute' could not be found (are you missing a using directive or an assembly reference?)
  • error CS0246: The type or namespace name 'ObsoletedInOSPlatformAttribute' could not be found (are you missing a using directive or an assembly reference?)

Example run-time error:

Unhandled exception. System.TypeLoadException: Could not load type 'System.Runtime.Versioning.MinimumOSPlatformAttribute' from assembly 'System.Runtime, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

To resolve these errors:

  • Update any references of MinimumOSPlatformAttribute to SupportedOSPlatformAttribute.
  • Update any references of RemovedInOSPlatformAttribute to UnsupportedOSPlatformAttribute.
  • Remove any references to ObsoletedInOSPlatformAttribute.
  • Rebuild your project (or perform clean + build) to delete old build artifacts.

Affected APIs

  • System.Runtime.Versioning.MinimumOSPlatformAttribute
  • System.Runtime.Versioning.ObsoletedInOSPlatformAttribute
  • System.Runtime.Versioning.RemovedInOSPlatformAttribute