FormatException：无法从 BsonType 'ObjectId' 反序列化 'Guid'

Question

I have been going crazy this last days.

I'm trying to use string Guids as _id's in my MongoDb, with the latest version of the driver. I stumbled with this tutorial, which shed me some light...

Storing GUIDs as strings in MongoDB with C#

But I am getting this error: FormatException: Cannot deserialize a 'Guid' from BsonType 'ObjectId'.

   MongoDB.Bson.Serialization.Serializers.GuidSerializer.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
MongoDB.Bson.Serialization.Serializers.SerializerBase<TValue>.MongoDB.Bson.Serialization.IBsonSerializer.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize(IBsonSerializer serializer, BsonDeserializationContext context)
MongoDB.Bson.Serialization.BsonClassMapSerializer<TClass>.DeserializeMemberValue(BsonDeserializationContext context, BsonMemberMap memberMap)

The stack trace:

 at MongoDB.Bson.Serialization.BsonClassMapSerializer`1.DeserializeMemberValue(BsonDeserializationContext context, BsonMemberMap memberMap)
   at MongoDB.Bson.Serialization.BsonClassMapSerializer`1.DeserializeClass(BsonDeserializationContext context)
   at MongoDB.Bson.Serialization.BsonClassMapSerializer`1.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
   at MongoDB.Bson.Serialization.IBsonSerializerExtensions.Deserialize[TValue](IBsonSerializer`1 serializer, BsonDeserializationContext context)
   at MongoDB.Driver.Core.Operations.CursorBatchDeserializationHelper.DeserializeBatch[TDocument](RawBsonArray batch, IBsonSerializer`1 documentSerializer, MessageEncoderSettings messageEncoderSettings)
   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.CreateFirstCursorBatch(BsonDocument cursorDocument)
   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.CreateCursor(IChannelSourceHandle channelSource, BsonDocument commandResult)
   at MongoDB.Driver.Core.Operations.FindCommandOperation`1.Execute(RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.FindOperation`1.Execute(RetryableReadContext context, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.FindOperation`1.Execute(IReadBinding binding, CancellationToken cancellationToken)
   at MongoDB.Driver.OperationExecutor.ExecuteReadOperation[TResult](IReadBinding binding, IReadOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.ExecuteReadOperation[TResult](IClientSessionHandle session, IReadOperation`1 operation, ReadPreference readPreference, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.ExecuteReadOperation[TResult](IClientSessionHandle session, IReadOperation`1 operation, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.FindSync[TProjection](IClientSessionHandle session, FilterDefinition`1 filter, FindOptions`2 options, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.<>c__DisplayClass45_0`1.<FindSync>b__0(IClientSessionHandle session)
   at MongoDB.Driver.MongoCollectionImpl`1.UsingImplicitSession[TResult](Func`2 func, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoCollectionImpl`1.FindSync[TProjection](FilterDefinition`1 filter, FindOptions`2 options, CancellationToken cancellationToken)
   at MongoDB.Driver.FindFluent`2.ToCursor(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.AsyncCursorSourceEnumerableAdapter`1.GetEnumerator()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at System.Linq.SystemCore_EnumerableDebugView`1.get_Items()

I've scoured the Internet in search of an answer.

I DO NOT WANT TO USE POCO's DECORATION, OR RETURN BsonDocuments . Already went this route:

BsonDefaults.GuidRepresentationMode = GuidRepresentationMode.V3;
            BsonSerializer.RegisterSerializer<Guid>(new GuidSerializer(GuidRepresentation.Standard));

and didn't work. Also did the convention thing...

public class GuidAsStringRepresentationConvention : ConventionBase, IMemberMapConvention
    {
        public void Apply(BsonMemberMap memberMap)
        {
            if (memberMap.MemberType == typeof(Guid))
                memberMap.SetSerializer(new GuidSerializer(BsonType.String));
            
            else if (memberMap.MemberType == typeof(Guid?))
                memberMap.SetSerializer(new NullableSerializer<Guid>(new GuidSerializer(BsonType.String)));
        }
    }

Didn't work either...

This is my code:

public class TestClass
    {
        public Guid Id { get; set; }
        public string Name { get; set; }
        public bool IsActive { get; set; }
    }

This gets called BEFORE the Db connection:

if (!BsonClassMap.IsClassMapRegistered(typeof(TestClass)))
        {
            BsonClassMap.RegisterClassMap<TestClass>(cm =>
            {
                cm.MapIdMember(m => m.Id).SetOrder(0);
                cm.MapMember(m => m.Name).SetOrder(1);
                cm.MapMember(m => m.IsActive).SetOrder(2);
            });
        }

var conn = configuration.GetConnectionString("MongoDb");
            var name = MongoUrl.Create(conn).DatabaseName;
            var client = new MongoClient(conn);
            _db = client.GetDatabase(name); 

after that, I try to get the records, after I initialize the collection in the constructor...

public async Task<IEnumerable<TestClass>> ReadAllAsync(CancellationToken cancellationToken = default)
        {
            var filter = Builders<TestClass>.Filter.Empty;
            var items = await _collection.Find<TestClass>(filter).ToListAsync(cancellationToken: cancellationToken);

            return items;
        }

And of course, I initialize the serializer on "ConfigureServices" in the Startup.cs

BsonSerializer.RegisterSerializer(new GuidSerializer(BsonType.String));

Last, the BSON document with the string GUID (or UUID):

{ 
    "_id" : "c2ea54fc-3942-4ad5-8315-9e96cc5de034", 
    "name" : "I'm Going Crazy", 
    "isActive" : true
}

If anyone can shed some light, I would appreciate it a lot. Thanks!!!!

[UPDATE]

I did this:

var col = _db.GetCollection<BsonDocument>("TestCollection");
var list = col.Find(FilterDefinition<BsonDocument>.Empty).ToList();

...and I can see the string GUIDs, everything loads perfectly. It's just NOT PARSING correctly. AND I DON'T KNOW WHY. And I refuse to parse this document manually!!!! That's what the driver is supposed to be doing!

[UPDATE 2]

Decided to decorate the property with:

[BsonId]
[BsonRepresentation(MongoDB.Bson.BsonType.String)]
public Guid Id { get; set; }

Didn't work either...

Answer 1

If you want to keep using Guids natively (rather than treating them as strings), change the serializer you are registering.

Remove:

BsonSerializer.RegisterSerializer(new GuidSerializer(BsonType.String));

And replace it with:

BsonSerializer.RegisterSerializer(new GuidSerializer(GuidRepresentation.Standard));
BsonDefaults.GuidRepresentationMode = GuidRepresentationMode.V3;

Yes, the second line (at time of writing), is an obsolete method, but for now it's the only way to do it. It's an open bug with the c# driver .

There does seem to be an issue here that needs to be fixed.

In the long run we encourage everyone to use the new V3 GuidRepresentationMode, and in fact when using V3 mode this bug does not appear to happen. I added the following line of code as the first line of main:

 BsonDefaults.GuidRepresentationMode = GuidRepresentationMode.V3;

We still need to figure out how to get your code to work in V2 mode, but if you are willing to use V3 mode you could have an immediate workaround.

Answer 2

Apparently, the GUIDs I was using were not valid GUIDs. I generated them using an online generator.

I generated new ones on another website, and voilá. Everyting worked.