HRESULT AddProp(
const WCHAR* wszName,
VARTYPE vtType,
long lOffset,
void *pDefValue);
Parameters
wszName
Pointer to the property name, used for PropertyBag persisting. This pointer must be constant data and must not change during the lifetime of the object.
wtType
Variant data type of the property. The following property types are supported.
| Property type | Description |
| VT_BOOL | Use for properties of VARIANT_BOOL. |
| VT_I2 | Use for numeric properties of type short. |
| VT_I4 | Use for numeric properties of type long or integer. |
| VT_R4 | Use for numeric properties of type float. |
| VT_R8 | Use for numeric properties of type double. |
| VT_LPWSTR | Use for wide string properties. |
| VT_LPSTR | Use for ANSI/multibyte string properties. |
| VT_BSTR | Use for BSTR string properties (Basic strings). |
| VT_UNKNOWN | Use for interface properties that support IPersistStream and IPersistPropertyBag and are co-creatable. For example, IFont and IPicture are interfaces that meet these requirements. |
lOffset
Offset to property in the user data buffer. This is unique among the properties. If a property is already added with the same offset, then the latter add will replace the former.
pDefValue
The default value of the property. Properties are not persisted if the current value matches the default value. Depending on the property data type, this argument is interpreted as follows.
| Property type | Description |
| VT_BOOL | Pointer to VARIANT_BOOL; the value is copied. |
| VT_I2 | Pointer to a short; the value is copied. |
| VT_I4 | Pointer to a long; the value is copied. |
| VT_R4 | Pointer to a float; the value is copied. |
| VT_R8 | Pointer to a double; the value is copied. |
| VT_LPWSTR | Pointer to the string data; the pointer is stored and referenced as needed. |
| VT_LPSTR | Pointer to the string data; the pointer is stored and referenced as needed. |
| VT_BSTR | Pointer to the string data; the pointer is stored and referenced as needed. |
| VT_UNKNOWN | Pointer to a CLSID; the pointer is stored and referenced as needed. |
Returns
S_OK
Method succeeded.
E_OUTOFMEMORY
Returned if allocation failed.
E_INVALIDARG
Returned if the Variant type is not supported.
Comments
Adds a property to the persistence collection.
For VT_UNKNOWN, pDefValue must point to an IID for the interface object. After a load, the IUnknown is QI for the interface identified by the given IID, and is stored at the specified offset in the user buffer.
Property offsets are offsets within a contiguous buffer kept by the caller. A property offset can be an offset to a data member within a class or a data member within a structure. Regardless, for each CPersistProperties collection, the offsets must be within the same buffer. The buffer and the buffer size are passed to the Load and Save methods for persistence.