Attributes recognized by the compiler in binaries

[jnm2]

Type of issue

Missing information

Description

As opposed to https://github.com/dotnet/docs/issues/43109, these attributes are generally disallowed in source. They affect the language meaning of compiled binaries, and thereby affect how the source code is compiled which references such binaries. This is of interest when using reflection or examining assemblies for purposes of understanding the language meaning of things in metadata.

It could also be interesting to list modreq and modopt types, which are not (usually) also attributes. They are part of the same theme as this page.

• CompilerFeatureRequired - Prevents downlevel compilers from using metadata they can't safely understand.

• DecimalConstantAttribute - Encodes const decimal fields since the runtime does not support decimal values as constant values.

• DefaultMemberAttribute - Encodes indexers with IndexerNameAttribute. This is how the correct indexer is recognized as default when its name has been customized. Allowed in source.

• DynamicAttribute - Encodes whether a type in a signature is dynamic (versus object).

• Microsoft.CodeAnalysis.EmbeddedAttribute - Types annotated with this attribute are ignored during lookup by the C# compiler. The compiler applies this to types that it generates as internal when compiling. This keeps the generated internal types from affecting other compilations when InternalsVisibleTo is used. Always generated, not in BCL. (References: https://github.com/dotnet/roslyn/pull/18715, https://github.com/dotnet/roslyn/issues/68697#issuecomment-1608216658)

• ExtensionAttribute - Encodes extension methods, and is also placed on their containing classes.

• FixedBufferAttribute - Encodes fixed struct fields.

• IsByRefLikeAttribute - Encodes a ref struct.

• IsReadOnlyAttribute - Indicates whether a parameter is in (versus readonly ref or [In] ref).

• IsUnmanagedAttribute - Encodes an unmanaged constraint on a type parameter.

• NativeIntegerAttribute - Encodes nint/nuint when runtime doesn't support native int. Always generated, not in BCL: https://github.com/dotnet/runtime/issues/38683.

• NullableAttribute, NullableContextAttribute, NullablePublicOnlyAttribute - Encode nullability annotations.

• ParamArrayAttribute - Encodes params on array parameters.

• ParamCollectionAttribute - Encodes params on non-array parameters. Part of the params collections language feature.

• RefSafetyRulesAttribute - Encodes a version that is required in order to understand ref safety annotations in the assembly. Part of the low-level struct improvements language feature.

• RequiredMemberAttribute - Encodes required on a member. Part of the required members language feature.

• RequiresLocationAttribute - Encodes whether a parameter is readonly ref (versus in or [In] ref).

• TupleElementNamesAttribute - Encodes tuple element names used in signatures.

Page URL

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/general

Content source URL

https://github.com/dotnet/docs/blob/main/docs/csharp/language-reference/attributes/general.md

Document Version Independent Id

6a60a627-c59c-74de-ce5b-6f52e15e7668

Article author

@BillWagner

Metadata

• ID: d415a929-c112-ab86-cf2e-13bf2ef64e1a
• Service: dotnet-csharp
• Sub-service: lang-reference

Related Issues