I would see this answer I wrote on another question.
int trackingID;
skeletonTracked = new Skeleton();
bool first = true;
Skeleton skeleton;
Skeleton[] skeletons = new Skeleton[6];
...
public void AllFramesReady(object sender, AllFramesReadyEventArgs e)
{
using (SkeletonFrame sFrame = e.OpenSkeletonFrame())
{
sFrame.CopySkeletonDataTo(skeletons);
skeleton = (from s in skeletons where s.TrackingState == SkeletonTrackingState.Tracked select s).FirstOrDefault();
if (skeleton == null)
return;
if (skeleton.TrackingState == SkeletonTrackingState.Tracked)
{
if (first)
{
skeletonTracked = skeleton;
trackingId = skeleton.TrackingID;
...
first = false;
}
if (skeleton.TrackingID == trackingId)
{
...
}
}
}