Try the following :
#
public void Updates(AUnit _aUnit, int Id)
{
int count = (int) _aUnit.ReadBits(8);
for (int i = 0; i < (int) count; i++)
{
ImageDetails _details = new ImageDetails(_aUnit, Id);
_details.ID = (int) _aUnit.ReadBits(8);
_details.Version = (int) _aUnit.ReadBits(8);
_details.set = (int) _aUnit.ReadBits(24);
newData.Add(_details);
}
_details.Rset = _aUnit.Buffer.Skip(10).Take(_details.set).ToArray();
_details.UpdateTime = DateTime.Now.ToString("h:mm:ss tt");
}
the difference now is that you create an entry for your collection inside the Loop and add each of those created entries to your collection (also inside the Loop)