使用MongoDB C＃驱动程序读取多种类型

Question

我尝试创建一个时间线集合，该集合可以托管多种类型。我没有问题插入类型或读取特定类型。但是，当我想要特定用户的所有类型列表时，我会出现问题。

public interface ITimelineItem
{
    public string EventType { get; set; }
    public string EventId { get; set; }
    public Guid UserId { get; set; }
}

public class TimelineItemBase
{
    public string EventType { get; set; }
    public string EventId { get; set; }
    public Guid UserId { get; set; }
    public List<MediaInfo> Media { get; set; }
}

public class AlbumEvent : TimelineItemBase, ITimelineItem
{
    public MediaAlbum Album { get; set; }
}

public class BirthdayEvent : TimelineItemBase, ITimelineItem
{
}

public class BlogPostEvent : TimelineItemBase, ITimelineItem
{
    public BlogPost Post { get; set; }
}

public static class TimelineRepo
{
    private static IMongoCollection<T> GetCollection<T>() where T : ITimelineItem
    {
        return Connection.Database.GetCollection<T>("Timeline");
    }

    public static async Task Add<T>(T data) where T : ITimelineItem
    {
        data.EventType = typeof(T).Name;

        var coll = GetCollection<T>();
        await coll.InsertOneAsync(data);
    }

    public static async Task<List<T>> GetEventsByUserId<T>(Guid userId) where T : ITimelineItem
    {
        return await GetCollection<T>().Find(p => p.UserId == userId).ToListAsync();
    }
}


public class GenerateTimeline
{
    public static async Task<List<ITimelineViewModel>> GetTimeline(Guid userId)
    {
        var items = await TimelineRepo.GetEventsByUserId<???>(userId);

        foreach (var item in items)
        {
            if (item is BirthdayEvent be)
            {
                // do work
            }
            else if (item is BlogPostEvent bp)
            {
                // do work
            }
            else if (item is AlbumEvent ae)
            {
                // do work
                ae.Album.Header
            }
        }
    }
}


[HttpGet("/api/user/{userid}/timeline"), Authorize]
public async Task<List<ITimelineViewModel>> GetTimeline(Guid userId)
{
    return await GenerateTimeline.GetTimeline(userId);
}

如何获得包含用户不同类型的列表？还是这是为用户创建时间表的不好方法？