title: How do I query in TFS to get work items with specified conditions for ALL OF its childs
body: <p>In <code>TFS query builder</code>, I need a query to get all PBIs that <strong>ALL</strong> of its child tasks are in done state.
  for example :</p>
  
  <pre><code>PBI : User Story 1
      - Task 1 (Done)
      - Task 2 (Done)
      - Task 3 (Done)
  
  PBI : User Story 2
      - Task 1 (Done)
      - Task 2 (Done)
      - Task 3 (In Progress)
  </code></pre>
  
  <p>In above example, the desired query should only returns <code>User Story 1</code></p>