使用 C# 反序列化 MongoDB 中的接口 - 未知的鉴别器值 [英] Deserializing interface in MongoDB using C# - Unknown discriminator value

问题描述

首先，我使用当前版本的 MongoDB (3.2) 及其 C#-driver (2.2.3).我有以下课程:

First of all, I use the current version of MongoDB (3.2) and its C#-driver (2.2.3). I have the following classes:

public class Item
{
    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }
    // ... some other properties

    public Data Data { get; set; }
}

public class Data
{
    public string BaseType { get; set; }
    public IBaseData BaseData { get; set; }
}

public interface IBaseData 
{
    string Name { get; set; }
    int Version { get; set; }
    IDictionary<string, object> PayloadData { get; }
}

然后我有一些不同的 IBaseData 接口实现:

Then I have some different implementations of the IBaseData interface:

public class EventData : IBaseData
{
    public int Version { get; set; }
    public string Name { get; set; }
    public IDictionary<string, object> PayloadData { get; set; }
    public IDictionary<string, object> Properties { get; set; }
}

public class ExceptionData : IBaseData
{
    // Implementation of the interface and some additional properties
}

将一个 Item-object 存储到 MongoDB 是没有问题的，看起来一切都是正确的.Mongo 使用 _t 来确定 IBaseData 的类型(例如 EventData).当我第一次尝试检索数据时，它运行良好，这意味着我拥有完整的对象树.当我重新启动应用程序并再次发布相同的请求时，出现以下错误:

Storing an Item-object to MongoDB is no problem and it seems that everything is correct. Mongo uses the _t to determine the type of IBaseData (e.g. EventData). When I try to retrieve the data for the first time, it works perfectly which means I have the complete tree of objects. When I restart the application and post the same request again, I get the following error:

反序列化类 Domain.Objects.Item 的 Data 属性时出错:反序列化类 Domain.Objects.Data 的 BaseData 属性时出错:未知鉴别器值EventData".

An error occurred while deserializing the Data property of class Domain.Objects.Item: An error occurred while deserializing the BaseData property of class Domain.Objects.Data: Unknown discriminator value 'EventData'.

删除 Mongo 数据库并启动应用程序后，它再次按预期工作.

After dropping the Mongo-database and starting the application, it works again as expected.

Google 给了我不同的方法，但没有任何帮助:

Google gave me different approaches but nothing helped me:

将具有多态值的字典存储在mongoDB 使用 C#

未知鉴别器值MyEvent"

将对象反序列化为接口使用 MongoDB C# 驱动程序

我想使用像 [BsonKnownTypes(typeof(Type1), typeof(Type2)] 这样的属性注释，但这仅适用于类.

I would like to work with property annotations like [BsonKnownTypes(typeof(Type1), typeof(Type2)], but this just works for classes.

你有什么想法吗?

推荐答案

我通过在 Program.cs(或其他应用程序启动类)中添加类映射为我部分解决了问题:

I partially solved the problem for me by adding a classmap in Program.cs (or other application-start class):

        BsonClassMap.RegisterClassMap<EventData>(cm =>
        {
            cm.AutoMap();
            cm.SetDiscriminator("EventData");
        });

        BsonClassMap.RegisterClassMap<ExceptionData>(cm =>
        {
            cm.AutoMap();
            cm.SetDiscriminator("ExceptionData");
        });

如果有人找到使用注释的方法，请回答这个问题.

If somebody find a way to work with annotations, please answer to this question.

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