The Format Version value is a WORD data type that is used to indicate the format version of this stream. It may be zero or one. The format-version indicator should be checked when reading the property set. If it is not zero or one, then the stream was written to a different specification and cannot be read by code developed according to this specification.
Property sets with Format Version 1 are equivalent to Version 0, with the following additions:
- Case sensitive property names. Property names are stored in the reserved dictionary property, Property ID 0. In version 1 property sets, these names can be case sensitive. Case sensitivity is determined by the reserved Behavior property, Property ID 0x80000003.
- Long property names. Version 1 property sets, unlike version 0 property sets, are not limited in the length of property names. See Property ID 0 for more information on property names.
- Property types. Version 1 property sets can hold all the property types that can be held in a version 0 property set plus some additional types. See the PROPVARIANT structure for more information on these types.