[Breaking change]: EnumConverter validates registered types to be enum

[LakshanF]

Description

EnumConverter is a type converter that converts to and from an enum type. EnumConverter now validates that the type to be registered is of an enum type.

Version

.NET 9 Preview 7

Previous behavior

The type to be registered was not validated to be an enum type.

New behavior

EnumConverter should be used only be used to convert to and from an enum type and will throw an ArgumentException if it is not. This also means that any derived classes of EnumConverter should also respect this requirement.

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

It seems logical to enforce the requirement that EnumConverter to be used to convert to and from enum types and likely an oversight not to do this earlier. However, the primary driving factor for this change was for trimming purposes. Trimming will not trim enum types but using EnumConverter for enum types required DynamicallyAccessedMembersAttribute annotation for an enum type. This meant using EnumConverter generates unnecessary trim warnings. There was a change this release to remove the annotation requirement. Part of this change was to enforce that EnumConverter should only be used with enums.

Recommended action

There is no easy workaround if an EnumConverter is used to convert to and from for a non-enum type.

Feature area

Extensions

Affected APIs

EnumConverter(Type) Constructor

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Associated WorkItem - 317208