IMetadataProvider Interface

The standard attribute metadata mechanism takes the names of public properties from an attribute and creates a dictionary of name/value pairs based on those properties, using that as the metadata for a service.

When you need to provide a more robust attribute-based definition of metadata, you can instead have your metadata attribute implement this interface. Rather than using name/value pairs generated by the properties on your attribute, you can directly provide the metadata key/value pairs to associate with a service.

This example shows what a metadata attribute might look like when providing custom metadata:

[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class)]
public class ProvidedMetadataAttribute : Attribute, IMetadataProvider
{
  public IDictionary<string, object> GetMetadata(Type targetType)
  {
    return new Dictionary<string, object>()
    {
      { "Key1", "Value1" },
      { "Key2", "Value2" }
    };
  }
}

Reference