Custom Key Mapping

By default, subjects are used directly as registry keys. String subjects are mapped to a StringSubjectKey for consistent handling. You can customize this mapping for specific subject types.

ISubjectKeyMapper Interface

public interface ISubjectKeyMapper
{
    bool CanHandle(Type subjectType);
    object Map(object subject);
}

Registering Mappers

var scope = new CapabilityScope(new CapabilityScopeOptions
{
    SubjectKeyMappers = new[] { new CaseInsensitiveEmailMapper() }
});

Example: Case-Insensitive Email

public class CaseInsensitiveEmailMapper : ISubjectKeyMapper
{
    public bool CanHandle(Type subjectType) => subjectType == typeof(string);

    public object Map(object subject)
    {
        var email = (string)subject;
        return email.ToLowerInvariant();
    }
}

With this mapper, "User@Example.COM" and "user@example.com" map to the same registry entry.

Default Behavior

Without custom mappers, string subjects are wrapped in StringSubjectKey for consistent dictionary key behavior. All other types use their default GetHashCode() and Equals() implementations.

When to Use

Custom key mapping is rarely needed. Consider it when:

• You need case-insensitive or normalized key matching
• Your subjects have custom equality semantics that differ from their default implementation
• You're using domain objects as subjects and need a stable key across instances