title: Automapper - map parent-child relationship by key from the same collation
body: <p>I have a table structure in DB like this:</p>
  <pre><code>Id: 1;
  Name: 'Question 1',
  ParentId: 2
  ----
  Id: 2;
  Name: 'Question 1.1',
  ParentId: 3
  ----
  Id: 3;
  Name: 'Question 1.1.1',
  ParentId: null
  </code></pre>
  <p>as a result, I need to build a collection of parent-child like this:</p>
  <pre><code>Id: 1;
  Name: 'Question 1',
  Children: 
  [
   {
     Id: 2;
     Name: 'Question 1.1',
     Children: 
     [
      {
       Id: 3;
       Name: 'Question 1.1.1'
      }
     ]
   }
  ]
  </code></pre>
  <p>I'm using EF to fetch all this data from the DB and build this parent-child relationship on the C# side. The question is if it's possible to build the same relationship with Automapper ProjectTo? If it's not possible with Automapper, any idea how to build LINQ to SQL query for this to aggregate on this data on the SQL side?</p>