You may have noticed that most of the PROPVARIANT helpers return an HRESULT.  This makes them easy to use in conjunction with COM calling patterns like the following:

IPropertyStore pps = ...
PROPVARIANT propvar = {0};
HRESULT hr = InitPropVariantFromInt32(100, &propvar);
if (SUCCEEDED(hr))
{
    hr = pps->SetValue(PKEY_Rating, propvar);
    if (SUCCEEDED(hr))
    {
        wprintf(L"Success!\n");
    }

    PropVariantClear(&propvar);
}

This works great for functions that already use HRESULTs.  But what if you just happen to absolutely know that the only VARTYPE your function will every see will be VT_UI4 every time the function is ever called?  Couldn't you just, say, read a member variable directly without checking the VARTYPE?  Well, you could, but would you take such a chance with the following helpers available for you to use?

// These will attempt to convert to the desired type, returning the provided default value if that isn't possible:
PSSTDAPI_(BOOL) PropVariantToBooleanWithDefault(REFPROPVARIANT propvarIn, BOOL fDefault);   // VT_BOOL
PSSTDAPI_(SHORT) PropVariantToInt16WithDefault(REFPROPVARIANT propvarIn, SHORT iDefault);   // VT_I2
PSSTDAPI_(USHORT) PropVariantToUInt16WithDefault(REFPROPVARIANT propvarIn, USHORT uiDefault);   // VT_UI2
PSSTDAPI_(LONG) PropVariantToInt32WithDefault(REFPROPVARIANT propvarIn, LONG lDefault);   // VT_I4
PSSTDAPI_(ULONG) PropVariantToUInt32WithDefault(REFPROPVARIANT propvarIn, ULONG ulDefault);   // VT_UI4
PSSTDAPI_(LONGLONG) PropVariantToInt64WithDefault(REFPROPVARIANT propvarIn, LONGLONG llDefault);   // VT_I8
PSSTDAPI_(ULONGLONG) PropVariantToUInt64WithDefault(REFPROPVARIANT propvarIn, ULONGLONG ullDefault);   // VT_UI8
PSSTDAPI_(DOUBLE) PropVariantToDoubleWithDefault(REFPROPVARIANT propvarIn, DOUBLE dblDefault);   // VT_R8

PropVariantToStringWithDefault is a little different.  It will NOT attempt to make a conversion.  It will return a direct pointer to the string data, or the provided default if that isn't possible.

PSSTDAPI_(PCWSTR) PropVariantToStringWithDefault(REFPROPVARIANT propvarIn, __in_opt LPCWSTR pszDefault);   // VT_LPWSTR or VT_BSTR

Again, these functions come from propvarutil.h and are implemented in propsys.dll.