c# - MongoDB C# 驱动程序 - 将集合序列化为接口(interface)

Question

由于工作环境的限制，我在 MongoDB 中实现了一个粗略的事件源存储。我正在尝试获取 IClientEvents 的列表像这样来自Mongo:

 var events = await _db.GetCollection<IClientEvent>("ClientEvents").FindAsync(c => c.ClientId == clientId);

运行上述存储库方法时出现以下异常:

Message: System.InvalidOperationException : {document}.ClientId is not supported.

IClientEvent接口(interface)定义为:

public interface IClientEvent
{
    Guid Id { get; set; }
    long TimeStamp { get; set; }
    Guid ClientId { get; set; }
}

public class ClientChangedEvent : IClientEvent
{
    public Guid Id { get; set; }
    public long TimeStamp { get; set; }
    public Guid ClientId { get; set; }

    public IEnumerable<Change> Changes;
    // ... other properties for the event
}

将有许多不同的事件类型存储到一个集合中，所有这些都将实现 IClientEvent .我只想在一次调用中获取 clientId 发生在客户端上的所有事件.

我已经注册了 IClientEvent 的所有具体实现。甚至添加了一个自定义鉴别器:

        var clientEventsDiscriminator = new ClientEventsMongoDiscriminatorConvention();
        BsonSerializer.RegisterDiscriminatorConvention(typeof(IClientEvent),clientEventsDiscriminator);
        BsonClassMap.RegisterClassMap<ClientChangedEvent>();
        BsonSerializer.RegisterDiscriminatorConvention(typeof(ClientChangedEvent), clientEventsDiscriminator);

我什至尝试注册 ImpliedImplementationInterfaceSerializer如 this SO post 中所述但是当我注册我已经为 IClientEvent 注册序列化程序的第二个具体实现时，它会引发异常.

不知道从这里去哪里。任何帮助是极大的赞赏!

-- 编辑更多代码:

这是完整的注册码:

        var clientEventsDiscriminator = new ClientEventsMongoDiscriminatorConvention();
        BsonSerializer.RegisterDiscriminatorConvention(typeof(IClientEvent),clientEventsDiscriminator);

        clientEventsDiscriminator.AddEventType<ClientChangedEvent>();
        BsonClassMap.RegisterClassMap<ClientChangedEvent>();
        BsonSerializer.RegisterDiscriminatorConvention(typeof(ClientChangedEvent), clientEventsDiscriminator);

        clientEventsDiscriminator.AddEventType<ClientAddedEvent>();
        BsonClassMap.RegisterClassMap<ClientAddedEvent>();
        BsonSerializer.RegisterDiscriminatorConvention(typeof(ClientAddedEvent), clientEventsDiscriminator);

这是鉴别器:

    public class ClientEventsMongoDiscriminatorConvention : IDiscriminatorConvention
{
    private Dictionary<string, Type> _eventTypes = new Dictionary<string, Type>();

    public string ElementName => "_eventType";

    public BsonValue GetDiscriminator(Type nominalType, Type actualType)
    {
        return GetDiscriminatorValueForEventType(actualType);
    }

    public Type GetActualType(IBsonReader bsonReader, Type nominalType)
    {
        var bookmark = bsonReader.GetBookmark();
        bsonReader.ReadStartDocument();
        if (!bsonReader.FindElement(ElementName))
        {
            throw new InvalidCastException($"Unable to find property '{ElementName}' in document. Cannot map to an EventType.");
        }

        var value = bsonReader.ReadString();
        bsonReader.ReturnToBookmark(bookmark);

        if (_eventTypes.TryGetValue(value, out var type))
        {
            return type;
        }

        throw new InvalidCastException($"The type '{value}' has not been registered with the '{nameof(ClientEventsMongoDiscriminatorConvention)}'.");
    }

    private string GetDiscriminatorValueForEventType(Type type)
    {
        var indexOfEventWord = type.Name.IndexOf("Event");
        if (indexOfEventWord == -1)
        {
            return type.Name;
        }
        return type.Name.Substring(0, indexOfEventWord);
    }

    public void AddEventType<T>()
    {
        var discriminatorName = GetDiscriminatorValueForEventType(typeof(T));
        _eventTypes.TryAdd(discriminatorName, typeof(T));
    }
}

运行代码时，它似乎从未命中 GetActualType判别器的方法。

Answer 1

我设法通过简单地更改 IClientEvent 让它工作。从接口(interface)到抽象类。