MongoDB error: Unable to determine actual type of object to deserialize for interface type

Question

I getting the following error when trying to execute a search query in C# MongoDB.

An exception of type 'System.FormatException' occurred in MongoDB.Bson.dll but was not handled in user code Additional information: An error occurred while deserializing the FOMessages property of class XYZ: Unable to determine actual type of object to deserialize for interface type IXYZ.

The code:

public interface IMessage
{
    MChannel Channel { get; }
}

MChannel is enum type.

public abstract class XYZ : IXYZ
{
    public List<IXYZ> FOMessages { get; set; }
}

Below is my search query in some method SearchXYZ .

MongoCursor<BsonDocument> searchMessages =
    context.GetDatabase()
           .GetCollection<BsonDocument>(typeof(Message).Name)
           .Find(Query.And(searchMongoQuery));

return searchMessages
         .ToList()
         .Select(message => DeserializeToTypedObject(message, (MChannel)(int)message["Channel"]))
         .ToList();

The DeserializeToTypedObject method:

private Message DeserializeToTypedObject(BsonDocument document, MChannel channel)
    {
        switch (channel)
        {
            case MChannel.EMAIL:
                return BsonSerializer.Deserialize<EmailMessage>(document);

            case MChannel.SMS:
                return BsonSerializer.Deserialize<SMSMessage>(document);

            case MChannel.VOICE:
                return BsonSerializer.Deserialize<VoiceMessage>(document);

            default:
                return null;
        }
    }

The code is failing in the method DeserializeToTypedObject .

Any clues?

Thanks in advance!!

Answer 1

I found the solution. We were inserting the object in string format so it was failing while retrieving from mongoDB