title: c# MongoDB driver: FindOneAndUpdate how to know if it has found a document?
body: <p>So I'm using the MongoDB driver to update an object field value in the database if the object exist.</p>
  
  <pre><code> IMongoDatabase db = _mongoClient.GetDatabase(DataBase);
   IMongoCollection&lt;Evento&gt; collection = db.GetCollection&lt;Evento&gt;(str_collection);
  
   collection.FindOneAndUpdate(
       e =&gt; e._id == eventoId &amp;&amp;
       e._visitantes.Any(v =&gt; v._empresa == empresa &amp;&amp;
           v._nombre == nombre &amp;&amp;
           v._apellidos == apellidos),
       Builders&lt;Evento&gt;.Update.Set(e =&gt; e._visitantes[-1]._asistido, true));
  </code></pre>
  
  <p>My question is: how I know that the object has found in the database? I have seen the documentation and I didn't found anything.</p>
  
  <p>In the case it doesn't exist, I don't want to create a new object, only I want to know if an object has found to change the value.</p>
  
  <p>Thanks.</p>