How to use findAndGetFloat64?

[xx_zx]

I am trying to use findAndGetFloat64 to get contour points in structure file.
My code is shown below:
const Float64* dataArray;
m_status = item->findAndGetFloat64Array(DCM_ContourData, dataArray);

However, I can not get any any value in the dataArray.
OFCondition shows following information:
theCondition = 0x00f5db98 ECC_IllegalCall {theCodeAndModule=65543 theStatus=OF_error theText=0x00dcd524 "Illegal Call, perhaps wrong parameters" }

Is there any thing wrong?

I know findAndGetFloat64 is also available, but it is low efficient to iterate all the points. I want to read all the points in a array at one time.

[Jörg Riesmeier]

Contour Data (3006,0050) has the value representation DS (Decimal String) and findAndGetFloat64Array() is only applicable to FD (Floating Point Double) as you can read in the API documentation.