MongoDB 自定义序列化程序未设置属性

Question

每当使用自定义序列化程序时，它都会在数据库中正确设置属性值，但对象上的属性保持默认值。

自定义序列化程序：

public class RngSerializer : SerializerBase<int>
{
    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, int value)
    {
        var rng = new Random().Next(0, 100);
        Console.WriteLine($"Generated rng {rng}");
        context.Writer.WriteInt32(rng);
    }
}

物体：

public class Entity
{
    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }
    
    [BsonSerializer(typeof(RngSerializer))]
    public int RngProp { get; set; }
}

执行插入的代码：

var entity = new Entity();
collection.InsertOne(entity);
Console.WriteLine($"Inserted Id {entity.Id}, Rng {entity.RngProp}");

可以看到调用了serializer，这个值也是在我检查数据库中的对象的时候设置的。 但是，驱动程序似乎没有正确设置该属性。

生成的 rng 32

插入的 ID 5e4ade582c509931f4467e38，Rng 0

Answer 1

我通过在插入发生之前触发序列化程序找到了解决方案；

        var bson = entity.ToBson();
        var hydrated = BsonSerializer.Deserialize<Entity>(bson);
        collection.InsertOne(hydrated);
        hydrated.Id = entity.Id;

并相应地更改序列化程序；

public class RngSerializer : SerializerBase<int>
{
    #region Overrides of SerializerBase<int>

    public override int Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        return context.Reader.ReadInt32();
    }

    #endregion

    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, int value)
    {
        //This part is important otherwise it will call the rng twice, once when the ToBson() is called and once when inserting.
        if (value == 0)
        {
            var rng = new Random().Next(0, 100);
            Console.WriteLine($"Generated rng {rng}");
            context.Writer.WriteInt32(rng);
        }
        else
        {
            context.Writer.WriteInt32(value);
        }
    }
}

它可能不是双序列化最优雅的方式，但它给了我预期的结果。

Answer 2

更新：将值传递给封装在引用类型中的序列化程序。

public class MyInt
{
    public int RngProp { get; set; }
}

public class Entity
{
    [BsonId]
    [BsonRepresentation(BsonType.ObjectId)]
    public string Id { get; set; }

    [BsonSerializer(typeof(RngSerializer))]
    public MyInt MyProp { get; set; } = new MyInt();
}

public class RngSerializer : SerializerBase<MyInt>
{
    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, MyInt value)
    {
        var rnd = new Random().Next(0, 100);
        value.RngProp = rnd;
        Console.WriteLine($"written rng {rnd}");
        context.Writer.WriteInt32(rnd);
    }

    public override MyInt Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        return new MyInt
        {
            RngProp = context.Reader.ReadInt32()
        };
    }
}


var entity = new Entity();
collection.InsertOne(entity);
Console.WriteLine($"Inserted Id {entity.Id}, Rng {entity.MyProp.RngProp}");

var result = collection.FindSync(e => e.Id == entity.Id).Single();
Console.WriteLine($"Retrieved Id {entity.Id}, Rng {result.MyProp.RngProp}");

Console.ReadLine();