How Can I Detect Face Using Emgucv

Image<Bgr, Byte> ImageFrame = capture.QueryFrame();

if (ImageFrame != null)   // confirm that image is valid
{
   //STEP 4.1-convert the image to gray scale
   Image<Gray, byte> grayframe = ImageFrame.Convert<Gray, byte>();

   MCvAvgComp[] faces = grayframe.DetectHaarCascade(haar, 1.4, 4,
      HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
      new Size(25, 25))[0];

   foreach (var face in faces)
   {
      ImageFrame.Draw(face.rect, new Bgr(Color.Green), 3);
   }
}
imageBox1.Image = ImageFrame;

pictureBox1.Image = ImageFrame.ToBitmap();
ImageFrame.Save(@"E:\9\MyPic.jpg");

//haar = new HaarCascade("haarcascade_frontalface_alt_tree.xml");