Summary

LINQ3 queries using ContainsKey on a Dictionary that is stored as DictionaryRepresentation.ArrayOfDocuments throws a ExpressionNotSupported exception.  ContainsKey support was added to dictionaries stored as DictionaryRepresentation.Document in CSHARP-4557 and this commit Support needed for the ArrayOfDocuments representation as well.

How to Reproduce

public class Model {
  [BsonDictionaryOptions(DictionaryRepresentation.ArrayOfDocuments)]
  public virtual Dictionary<string, string> Foo { get; set; }
}

collection.AsQueryable()
  .Where(x => x.Foo.ContainsKey("x")).ToList();

Additional Background

The LINQ2 code for this I found here