Nest Elasticsearch search for null value
<p>Using NEST (1.7.1) I have a specific search, where one field should match some collection of values OR this field should be null. Seems trival but I cannot create this query so the result would be the same as result when I'm not filtering my documents by this field. </p>

<p>Document:</p>

<pre><code>public class Document
{
    ...
    [ElasticProperty(Index = FieldIndexOption.NotAnalyzed)]
    public string Field{ get; set; }
}
</code></pre>

<p>Query to match any of values from given collection: </p>

<pre><code>Filter&lt;Document&gt;.Query(q =&gt;  q.Terms(p=&gt; p.Field, matchingCollection));
</code></pre>

<p>To match also those documents, which have NULL set as Field I was trying to add: </p>

<pre><code>matchingCollection.Add(string.Empty);
matchingCollection.Add("NULL");
</code></pre>

<p>But without any success. 
Any ideas ? Thank you :)</p>