PropVariantToBoolean function (propvarutil.h)

Extracts a Boolean property value of a PROPVARIANT structure. If no value can be extracted, then a default value is assigned.

Syntax

PSSTDAPI PropVariantToBoolean(
  [in]  REFPROPVARIANT propvarIn,
  [out] BOOL           *pfRet
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[out] pfRet

Type: BOOL*

When this function returns, contains the extracted property value if one exists; otherwise, contains FALSE.

Return value

Type: HRESULT

If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

This helper function is used in places where the calling application expects a PROPVARIANT to hold a Boolean value. For instance, an application obtaining 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 a conversion is not possible, PropVariantToBoolean will return a failure code and set pfRet to FALSE. See PropVariantChangeType for a list of possible conversions. Of note, VT_EMPTY is successfully converted to FALSE.

Examples

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

// IPropertyStore *ppropstore;
// Assume variable ppropstore is initialized and valid
PROPVARIANT propvar = {0};

HRESULT hr = ppropstore->GetValue(PKEY_IsShared, &propvar);
if (SUCCEEDED(hr))
{
     // PKEY_IsShared is expected to produce a VT_BOOL or VT_EMPTY value.
     // PropVariantToBoolean will convert VT_EMPTY to FALSE.
     BOOL fShared;
     
     hr = PropVariantToBoolean(propvar, &fShared);
     if (SUCCEEDED(hr))
     {
         // fShared is now valid
     }
     else
     {
         // fShared is always FALSE
     }
     
     PropVariantClear(&propvar);
}

                    

Requirements

See also

InitPropVariantFromBoolean

PropVariantGetBooleanElem

PropVariantToBooleanWithDefault

VariantToBoolean