PropVariantToUInt64WithDefault function (propvarutil.h)

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

Syntax

PSSTDAPI_(ULONGLONG) PropVariantToUInt64WithDefault(
  [in] REFPROPVARIANT propvarIn,
  [in] ULONGLONG      ullDefault
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[in] ullDefault

Type: ULONGLONG

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

Return value

Type: ULONGLONG

Returns the extracted unsigned LONGLONG value, or a default.

Remarks

This helper function is used in places where the calling application expects a PROPVARIANT to hold a ULONGLONG 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 ULONGLONG value for UInt64 properties.

If the source PROPVARIANT has type VT_UI8, this helper function extracts the ULONGLONG value. Otherwise, it attempts to convert the value in the PROPVARIANT structure into a ULONGLONG. If the source PROPVARIANT has type VT_EMPTY or a conversion is not possible, then PropVariantToUInt64WithDefault will return the default provided by ullDefault. 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 PropVariantToUInt64WithDefault to access a ULONGLONG value in a PROPVARIANT.

// IPropertyStore *ppropstore;
// Assume variable ppropstore is initialized and valid
PROPVARIANT propvar = {0};
HRESULT hr = ppropstore->GetValue(PKEY_Size, &propvar);
if (SUCCEEDED(hr))
{
     // PKEY_Size is expected to produce a VT_UI8 or VT_EMPTY value.
     // The application developer decided to treat VT_EMPTY or invalid values as 0
     ULONGLONG ullSize = PropVariantToUInt64WithDefault(propvar, 0);
     // ullSize is now valid.
     PropVariantClear(&propvar);
}

Requirements