ICustomTypeDescriptor, TypeDescriptionProvider, TypeConverter, and UITypeEditor

Tweaks:

• TypeDescriptionProvider

  • still replaces metadata (not extends)
  • can also be added be TypeDescriptor.AddProvider
  • can be applied per-type as well as per-instance, making it possible to apply to lists without having to implement ITypedList

• TypeConverter

  • for PropertyGrid, this is also the mechanism used to obtain metadata; note that ExpandableObjectConverter simply delegates to TypeDescriptor.GetProperties, but this is not always the case
  • also responsible for re-creating immutable objects (such as structs) with changes

• UITypeEditor

  • also responsible for painting the preview box in PropertyGrid

Additional:

• IExtenderProvider – appends properties; this may be what you were getting confused with TypeDescriptionProvider
• ITypedList – broadly the twin of ICustomTypeDescriptor, but for lists; can be avoided by use of TypeDescriptionProvider and a non-object indexer on any IList, i.e. public T this[int index] {get;}
• IListSource – provides indirection between a data-source and the data; for example, a DataTable implements IListSource, returning DefaultView when requested