Serialization error in MongoDb Dictionary property using RegEx

[danyolgiax]

Im trying to write the code filters a collection of documents with a property of type Dictionary<string,object>.

Code is the following:

var query = myCollection.AsQueryable();

var regex = new Regex("^Foo");

query = query.Where(x => regex.IsMatch(x.User["FullName"].ToString())); <--- Error here

running this code I get this error:

Unable to determine the serialization information for the expression: x.User.get_Item("FullName").ToString()

Document is declared in this way:

public class MyClass
{
    [BsonId]
    public ObjectId _id { get; set; }

    [BsonDictionaryOptions(DictionaryRepresentation.ArrayOfDocuments)] //Tryied also Dynamic, Document, ArrayOfArray
    public Dictionary<string, object> User { get; set; }
}

Debugging Driver source code I found something strange. In BsonSerializationInfoFinder class, node.Method.Name must be ElementAt or get_Item while in this case it is ToString and it returns null raising the exception!

protected override BsonSerializationInfo VisitMethodCall(MethodCallExpression node)
    {
        switch (node.Method.Name)
        {
            case "ElementAt":
                return VisitElementAt(node);
            case "get_Item":
                return VisitGetItem(node);
        }

        return null;
    }    

Is this a driver bug?

[danyolgiax]

I think I found the problem:

https://jira.mongodb.org/browse/CSHARP-917