<PackageReference Include="System.Threading.RateLimiting" Version="11.0.0-preview.2.26159.112" />

System.Threading.RateLimiting.MetadataName

public static class MetadataName
Contains some common metadata name-type pairs and helper method to create a metadata name.
public static MetadataName<string> ReasonPhrase { get; }

Metadata put on a failed lease acquisition to specify the reason the lease failed.

public static MetadataName<TimeSpan> RetryAfter { get; }

Metadata put on a failed lease acquisition to specify when to retry acquiring a lease. For example, used in TokenBucketRateLimiter which periodically replenishes leases.

public static MetadataName<T> Create<T>(string name)

Create a strongly-typed metadata name.