The IPropertyStorage interface manages the persistent properties of a single property set. Persistent properties consist of information that can be stored persistently in a property set, such as the summary information associated with a file. This contrasts with run-time properties associated with Controls and Automation, which can be used to affect system behavior. Use the methods of the IPropertySetStorage interface to create or open a persistent property set. An instance of the IPropertySetStorage interface can manage zero or more IPropertyStorage instances.

Each property within a property set is identified by a property identifier (ID), a four-byte ULONG value unique to that set. You can also assign a string name to a property through the IPropertyStorage interface.

Property IDs differ from the dispatch IDs used in Automation dispid property name tags. One difference is that the general-purpose use of property ID values zero and one is prohibited in IPropertyStorage, while no such restriction exists in IDispatch. In addition, while there is significant overlap among the data types for property values that may be used in IPropertyStorage and IDispatch, the property sets are not identical. Persistent property data types used in IPropertyStorage methods are defined in the PROPVARIANT structure.

The IPropertyStorage interface can be used to access both simple and nonsimple property sets. Nonsimple property sets can hold several complex property types that cannot be held in a simple property set. For more information see Storage vs. Stream for a Property Set.

Syntax

interface IPropertyStorage : IUnknown

When To Implement

Implement IPropertyStorage when you want to store properties in an object. If you are using the COM compound files implementation, the compound file object created through a call to StgCreateDocfile includes an implementation of IPropertySetStorage, which allows access to the implementation of IPropertyStorage. Once you have a pointer to any of the interface implementations (such as IStorage) on this object, you can call QueryInterface to get a pointer to the IPropertySetStorage interface implementation, and then call either the Open or Create method, as appropriate to obtain a pointer to the IPropertyStorage interface managing the specified property set.

When To Use

Use IPropertyStorage to create and manage properties that are stored in a given property set.

Methods

The IPropertyStorage interface inherits the methods of the IUnknown interface.

In addition, IPropertyStorage defines the following methods.

Requirements

See Also

Managing Properties
Property Storage Considerations
IPropertySetStorage
IEnumSTATPROPSTG
IEnumSTATPROPSETSTG
STATPROPSTG
STATPROPSETSTG
PROPVARIANT
IPropertyStorage-Compound File Implementation
IPropertyStorage-NTFS File System Implementation
IPropertyStorage-Stand-alone Implementation
Samples

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Build date: 8/12/2008