Problem with HogDescriptor in EMGU

[silviagiordano]

Hi everyone! I'm developing an object detection for a project interested in robotics. I've trained an Hog descriptor to be able to detect some boxes... When I've tried to use the constuctor public
HOGDescriptor(
Size winSize,
Size blockSize,
Size blockStride,
Size cellSize,
int nbins,
int derivAperture,
double winSigma,
double L2HysThreshold,
bool gammaCorrection
) hog;

-> HOGDescriptor des = new HOGDescriptor(new Size(64, 128), new Size(16, 16), new Size(8, 8), new Size(8, 8), 9, 0, -1, 0.2, true);

with a winSize(64, 64) for use my vector of float in
hog.SetSVMDetector(vector)

Visual studio give me a "NullReferenceException"... but I've instantiated both hog than vector! So why? I've failed in writing the constructor?