title: MongoDb "AnyIn" filter method in C# gives compiler error
body: <p>The following method tries to find documents in a Mongo collection with several filters using '&amp;' operator:</p>
  <pre><code>public MyEntity GetByUserRefsGuidDate(List&lt;OrgReference&gt; userRefs, string guid, DateTime date)
          {
              var userGuids = new List&lt;String&gt;();
              foreach (var userRef in userRefs)
                  userGuids.Add(userRef.Guid);
              var filterBuilder = Builders&lt;MyEntity&gt;.Filter;
              var filter = filterBuilder.Eq(e =&gt; e.IsAnswered, true) &amp;
                           filterBuilder.AnyIn(e =&gt; e.UserRef.Guid, userGuids) &amp;
                           filterBuilder.Eq(e =&gt; e.Guid, guid) &amp;
                           filterBuilder.Eq(e =&gt; e.Date, date);
  
          }
  </code></pre>
  <p>The <code>AnyIn</code> filter method gives me the following error:</p>
  <pre><code>Cannot convert lambda expression to type 'FilterDefinition&lt;MyEntity&gt;' 
  because it is not a delegate type.
  </code></pre>
  <p>Guids are just string values.
  MyEntity class:</p>
  <pre><code>public class MyEntity
      {
  
          [BsonId]
          [BsonIgnoreIfDefault]
          public ObjectId MongoId { get; set; }
  
          public string Title { get; set; }
  
          public string Guid { get; set; }
  
          public List&lt;Category&gt; Categories { get; set; }
  
          public OrgReference UserRef { get; set; }
  
          public bool IsAnswered { get; set; }
  
          [BsonDateTimeOptions(Kind = DateTimeKind.Utc)]
          public DateTime Date { get; set; }
  
      }
  </code></pre>
  <p>How do I solve this?</p>