title: Linq relational table include
body: <p>I have 4 relational table;</p>
  
  <ol>
  <li>Category</li>
  <li>Product</li>
  <li>ProductBrand</li>
  <li>ProductImage</li>
  </ol>
  
  <p>I need <code>linq</code> query included <em>3 tables</em> group by <code>ProductBrand from CategoryId</code>.</p>
  
  <p>I try this;</p>
  
  <pre><code>var PBrand = from b in db.ProductBrands
                         join p in db.Products on b.BrandId equals p.BrandId
                         join i in db.ProductImages on p.ProductId equals i.ProductId 
                         where b.CategoryId == 5
                         select b;
  </code></pre>
  
  <p>but <code>Products</code> and <code>ProductImages</code> are null. How I include <code>Products</code> and <code>ProductImages</code> table on <code>Brand</code> table?</p>