title: Mongo throwing "Element name 'name' is not valid' exception
body: <p>I'm updating a simple field.</p>
  
  <pre><code>var filterDocument = new BsonDocument { { "name", "alice" } };
  
  var newDocument = new BsonDocument { { "name", "Alice" } };
  
  collection.UpdateOne(filterDocument, newDocument);
  </code></pre>
  
  <p>But when I reach the the update statement I get an exception <code>{"Element name 'name' is not valid'."}</code></p>
  
  <p>What's wrong with that element name?</p>
  
  <p><strong>Update</strong></p>
  
  <p>Re-writing it to this:</p>
  
  <pre><code>var filterDocument = new BsonDocument { { "x", "alice" } };
  
  var newDocument = new BsonDocument { { "y", "Alice" } };
  
  collection.UpdateOne(filterDocument, newDocument);
  </code></pre>
  
  <p>Throw the exception <code>{"Element name 'y' is not valid'."}</code></p>
  
  <p>Also, <code>UpdateOne()</code> or <code>UpdateMany()</code> makes no difference.</p>
  
  <p>Also, from the shell it's fine.</p>
  
  <pre><code>&gt; db.crud.update({name:'alice'},{name:'Alice'})
  WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
  </code></pre>