title: MongoDB: Project to array item with minimum value of field
body: <p>Suppose my collection consists of items that looks like this:</p>
  
  <pre><code>{
      "items" : [
          {
              "item_id": 1,
              "item_field": 10
          },
          {
              "item_id": 2,
              "item_field": 15
          },
          {
              "item_id": 3,
              "item_field": 3
          },
      ]
  }
  </code></pre>
  
  <p>Can I somehow select the entry of <code>items</code> with the lowest value of <code>item_field</code>, in this case the one with <code>item_id</code> 3?</p>
  
  <p>I'm ok with using the aggregation framework. Bonus point if you can give me the code for the C# driver.</p>