MongoDB C# 2.1 ReplaceOneAsync not working for repository pattern

Question

I'm trying to implement async repository pattern for mongodb. This is my code:

public class EntityBase
{
    [BsonId]
    public ObjectId Id { get; set; }
}

public class User : EntityBase
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class MongoDbRepository<T> where T : EntityBase
{
    private IMongoDatabase _database;
    private IMongoCollection<T> _collection;

    public MongoDbRepository()
    {
        GetDatabase();
        GetCollection();
    }

    private void GetDatabase()
    {
        var client = new MongoClient("mongodb://localhost/");
        _database = client.GetDatabase("LocalTest");
    }

    private void GetCollection()
    {
        _collection = _database.GetCollection<T>(typeof(T).Name);
    }

    public async Task<ReplaceOneResult> Save(T doc)
    {
        return await _collection.ReplaceOneAsync(w => w.Id == doc.Id, doc, new UpdateOptions { IsUpsert = true });
    }
}

And console application which just calling the logic:

class Program
{
    static void Main(string[] args)
    {
        var userRepo = new MongoDbRepository<User>();

        userRepo.Save(new User
        {
            FirstName = "fn",
            LastName = "ln"
        }).Wait();

        Console.ReadKey();
    }
}

In this line of code:

return await _collection.ReplaceOneAsync(w => w.Id == doc.Id, doc, new UpdateOptions { IsUpsert = true });

I'm getting an error:

Convert([document]).Id is not supported.

If I'm changing the code like this, it's working:

private IMongoCollection<EntityBase> _collection;
    private void GetCollection()
    {
        _collection = _database.GetCollection<EntityBase>(typeof(EntityBase).Name);
    }

But I really need to use T instead of BaseMongoClass... Any ideas why this error occurs and how can I fix it? Thanks a lot!

Answer 1

Just solved the same problem. Get rid of the ==, for some reason the new mongo driver doesn't like it. I used .Equals()

Change

return await _collection.ReplaceOneAsync(w => w.Id == doc.Id, 
    doc, new UpdateOptions { IsUpsert = true });

To

return await _collection.ReplaceOneAsync(w => w.Id.Equals(doc.Id), 
    doc, new UpdateOptions { IsUpsert = true });