PropVariantToBooleanWithDefault function (propvarutil.h)

Extracts the Boolean property value of a PROPVARIANT structure. If no value exists, then the specified default value is returned.

Syntax

PSSTDAPI_(BOOL) PropVariantToBooleanWithDefault(
  [in] REFPROPVARIANT propvarIn,
  [in] BOOL           fDefault
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[in] fDefault

Type: BOOL

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

Return value

Type: BOOL

The extracted Boolean value or the default value.

Remarks

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

If the source PROPVARIANT has type VT_BOOL, this helper function extracts the Boolean value. Otherwise, it attempts to convert the value in the PROPVARIANT structure into a Boolean. If the source PROPVARIANT has type VT_EMPTY or a conversion is not possible, then PropVariantToBooleanWithDefault returns the default provided by fDefault. 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 PropVariantToBooleanWithDefault to access a Boolean value in a PROPVARIANT.

// IPropertyStore *ppropstore;
// Assume the variable ppropstore is initialized and valid.
PROPVARIANT propvar = {0};
HRESULT hr = ppropstore->GetValue(PKEY_IsRead, &propvar);

if (SUCCEEDED(hr))
{
     // PKEY_IsRead is expected to produce a VT_BOOL or VT_EMPTY value.
     // The application developer decided to treat VT_EMPTY or invalid values as TRUE
     BOOL fShared = PropVariantToBooleanWithDefault(propvar, TRUE);
     
     // fShared is now valid.
     PropVariantClear(&propvar);
}

Requirements