OptionalFullWhen true, the field spans the full width of the form, changing the layout from horizontal (label beside field) to vertical (label above field).
This is useful for fields with longer content like AdvancedTable or Attachment.
Internal name of the SharePoint field.
OptionalReadWhen true, the field becomes read-only.
OptionalTargetOptionalValidationApplies field validation.
You can also modify field's SharePoint properties (see SPField)