title: Find child objects in list of parent objects using LINQ
body: <p>Given a list of Parent objects that each have a list of Child objects, I want to find the child object matching a specific ID. </p>
  
  <pre><code>public class Parent
  {
      public int ID { get; set; }
      public List&lt;Child&gt; Children { get; set; }
  }
  
  public class Child
  {
      public int ID { get; set; }
  }
  </code></pre>
  
  <p>Now I want the Child object having a specific ID:</p>
  
  <pre><code>List&lt;Parent&gt; parents = GetParents();
  Child childWithId17 = ???
  </code></pre>
  
  <p>How can I do this using Linq?</p>