PropVariantToUInt32WithDefault function (propvarutil.h)

Extracts a ULONG value from a PROPVARIANT structure. If no value exists, then a specified default value is returned.

Syntax

PSSTDAPI_(ULONG) PropVariantToUInt32WithDefault(
  [in] REFPROPVARIANT propvarIn,
  [in] ULONG          ulDefault
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[in] ulDefault

Type: ULONG

Specifies a default property value, for use where no value currently exists.

Return value

Type: ULONG

Returns extracted ULONG value, or default.

Remarks

This helper function is used in places where the calling application expects a PROPVARIANT to hold a ULONG value and would like to use a default value if it does not. For instance, an application obtaining values from a property store can use this to safely extract the ULONG value for UInt32 properties.

If the source PROPVARIANT has type VT_UI4, this helper function extracts the ULONG value. Otherwise, it attempts to convert the value in the PROPVARIANT structure into a ULONG. If the source PROPVARIANT has type VT_EMPTY or a conversion is not possible, then PropVariantToUInt32WithDefault will return the default provided by ulDefault. See PropVariantChangeType for a list of possible conversions.

Examples

The following example, to be included as part of a larger program, demonstrates how to use PropVariantToUInt32WithDefault to access a ULONG value in a PROPVARIANT.

// IPropertyStore *ppropstore;
// Assume variable ppropstore is initialized and valid
PROPVARIANT propvar = {0};
HRESULT hr = ppropstore->GetValue(PKEY_Rating, &propvar);
if (SUCCEEDED(hr))
{
     // PKEY_Rating is expected to produce a VT_UI4 or VT_EMPTY value.
     // The application developer decided to treat VT_EMPTY or invalid values as 0
     ULONG uRating = PropVariantToUInt32WithDefault(propvar, 0);
     // uRating is now valid.
     PropVariantClear(&propvar);
}

Requirements

See also

InitPropVariantFromUInt32

PropVariantChangeType

PropVariantToUInt32

VariantToUInt32