title: How to use Linq to select and group complex child object from a parents list
body: <p>How to use Linq to select and group complex child object from a parents list.</p>
  
  <p>I have an <strong>OrderList</strong> each of order object has a <strong>OrderProductVariantList</strong>(OrderLineList), and each of <strong>OrderProductVariant</strong> object has ProductVariant, and then the <strong>ProductVariant</strong>  object will have a <strong>Product</strong> object which contains product information.</p>
  
  <p><strong>My goal is to select and group the most popular products from the order list.</strong> </p>
  
  <p>Can anyone help me with this?</p>
  
  <p>Many thanks.</p>