c# code errors out with the following when trying to generate explain plan when querying a collection using a compound wildcard index:
Unhandled exception. System.InvalidOperationException: Duplicate element name '$_path'.
   at MongoDB.Bson.BsonDocument.Add(BsonElement element)
   at MongoDB.Bson.BsonDocument.Add(String name, BsonValue value)
   at MongoDB.Bson.Serialization.Serializers.BsonDocumentSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonDocumentSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonDocumentSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonDocumentSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.Serializers.BsonDocumentSerializer.DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.Serializers.BsonValueSerializerBase`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.ProcessResponse(ConnectionId connectionId, CommandMessage responseMessage)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.SendMessageAndProcessResponse(CommandRequestMessage message, Int32 responseTo, IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.WireProtocol.CommandUsingCommandMessageWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.Server.ServerChannel.ExecuteProtocol[TResult](IWireProtocol`1 protocol, ICoreSession session, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.Server.ServerChannel.Command[TResult](ICoreSession session, ReadPreference readPreference, DatabaseNamespace databaseNamespace, BsonDocument command, IEnumerable`1 commandPayloads, IElementNameValidator commandValidator, BsonDocument additionalOptions, Action`1 postWriteAction, CommandResponseHandling responseHandling, IBsonSerializer`1 resultSerializer, MessageEncoderSettings messageEncoderSettings, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.CommandOperationBase`1.ExecuteProtocol(IChannelHandle channel, ICoreSessionHandle session, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.ExecuteAttempt(RetryableReadContext context, Int32 attempt, Nullable`1 transactionNumber, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.RetryableReadOperationExecutor.Execute[TResult](IRetryableReadOperation`1 operation, RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.Execute(RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.ReadCommandOperation`1.Execute(IReadBinding binding, CancellationToken cancellationToken)
   at MongoDB.Driver.OperationExecutor.ExecuteReadOperation[TResult](IReadBinding binding, IReadOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.ExecuteReadOperation[T](IClientSessionHandle session, IReadOperation`1 operation, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.RunCommand[TResult](IClientSessionHandle session, Command`1 command, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.<>c_DisplayClass49_0`1.<RunCommand>b_0(IClientSessionHandle session)
   at MongoDB.Driver.MongoDatabase.UsingImplicitSession[TResult](Func`2 func, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabase.RunCommand[TResult](Command`1 command, ReadPreference readPreference, CancellationToken cancellationToken)
   at MDBW2020AttributeVsWildcard.EqualityBenchmark.Main() in /Users/tc/Downloads/AttributePatternTestToolBox/AttributePatternTestToolBox/EqualityBenchmark.cs:line 270
   at MDBW2020AttributeVsWildcard.Program.Main(String[] args) in /Users/tc/Downloads/AttributePatternTestToolBox/AttributePatternTestToolBox/Program.cs:line 20

 

code is as follows:
publicvoidMain()

{   //Gets the Unix timestamp so we can use it as id stringunixTimestamp=Math.Floor((DateTime.UtcNow.Subtract(newDateTime(1970, 1, 1))).TotalSeconds).ToString(); Console.Out.WriteLine("Starting Benchmark."); Console.Out.WriteLine(String.Format("Timestamp of the benchmark: \{0}

", unixTimestamp));

//Gets the query shapes
QueryDocumentBatchbatch=GetQueryDocumentBatch(testCount);
classicAttributeQueries.AddRange(batch.classicAttributeQueries);
enhancedAttributeQueries.AddRange(batch.enhancedAttributeQueries);
dotNotationQueries.AddRange(batch.dotNotationQueries);
 
//Creates the find command document as it is a requirement for the explain command document
BsonDocumentfindCommand=newBsonDocument("find", sharedSettings.CompoundWildcardSubdocColl.CollectionNamespace.CollectionName);
findCommand["filter"] =dotNotationQueries[1];

//Creates the explain command
BsonDocumentexplainCommand=newBsonDocument("explain", findCommand);
explainCommand["verbosity"] ="executionStats";

//Runs the explain and returns the result
BsonDocumentexplainResult=sharedSettings.CompoundWildcardSubdocColl.Database.RunCommand<BsonDocument>(explainCommand);
Console.Out.WriteLine("explain: "+explainResult);
}

}
}