C#

VARIENT vtParam;
vtParam.vt = VT_ARRAY | VT_UI1;
vtParam.parray = //SAFEARRAY of type byte.

private double ParseString(string theString)
{
	// first, remove all non-numbers and non-decimal points from the string
	const char decimalPoint = '.';
	int numDigitChars = 0;
	bool foundDecimalPoint = false;

	foreach(char ch in theString)
	{
		if(char.IsNumber(ch))
			numDigitChars++;
		else if(ch == decimalPoint && !foundDecimalPoint)
		{
			foundDecimalPoint = true;
			numDigitChars++;
		}
		else break;
	}

	if(numDigitChars > 0)
		return double.Parse(theString.Substring(0, numDigitChars));
	else return 0;
}

...
// in some other function
string myDoubleString = "3.1457helloWorld";
double dbl = ParseString(myDoubleString);
Console.WriteLine(dbl); // outputs 3.1457

// this is managed c++ sample, just to get an idea how to retrieve properties

// call with: Guid fmtidSummary = new Guid("F29F85E0-4FF9-1068-AB91-08002B27B3D9");

HRESULT FileDocProps::ReadProps(String* fileName, Guid fmtid, IList* props)
{
	CStringW swFileName(fileName);

	FMTID iidFmtID;
	SetGUID(iidFmtID, fmtid);

	CComPtr<IPropertySetStorage> spPropSetStg;
	CComPtr<IPropertyStorage> spPropStg;

	HRESULT hr = S_OK;

	hr = StgOpenStorageEx(
		swFileName,
		STGM_READ | STGM_SHARE_EXCLUSIVE,
		STGFMT_ANY,
		0, NULL, NULL, 
		IID_IPropertySetStorage,
		reinterpret_cast<void**>(&spPropSetStg));

	if (FAILED(hr)) return hr;

	// try to open existing propset
	hr = spPropSetStg->Open(
		iidFmtID,
		STGM_READ | STGM_SHARE_EXCLUSIVE,
		&spPropStg);

	if (FAILED(hr)) return S_OK; // no property set found

	CComPtr<IEnumSTATPROPSTG> spEnum;

	// get codepage info

	bool isANSI = false;
	short codePage = 0;
	hr = GetCodePage(spPropStg, codePage, isANSI);
	if (FAILED(hr)) return hr;

	bool isUnicode = codePage == 0x04B0;

	// enum props

	hr = spPropStg->Enum(&spEnum);
	if (FAILED(hr)) return hr;

	STATPROPSTG sps;
	while (spEnum->Next(1, &sps, NULL) == S_OK)
	{
		PROPSPEC pss;
		PROPVARIANT pvs;

		pss.ulKind = PRSPEC_PROPID;
		pss.propid = sps.propid;

		hr = spPropStg->ReadMultiple(1, &pss, &pvs);
		if (FAILED(hr)) continue;

		// add item and copy value

		try
		{
			String* name = sps.lpwstrName ? new String(sps.lpwstrName) : 0;
			Object* v = PropVarToObject(pvs, codePage);

			PropInfo pi((int) pss.propid, name, v);

			props->Add(__box(pi));
		}
		catch(...)
		{
		}

		// clear
		PropVariantClear(&pvs);

		CoTaskMemFree(sps.lpwstrName);
		sps.lpwstrName = NULL;
	}

	return S_OK;
}