如何在MongoDB中使用ImmutableArray（C#）？

Question

我试图在MongoDB中保存ImmutableArray（System.Collections.Immutable）。

我试过MongoDB。Immutable，但它仅限于Immutable包的旧版本，不支持ImmutableArray。

我试图创建一个自定义序列化程序使用IBsonSeriazer和IBsonSeriazationProviderSeriazerBase没有成功。

[BsonSerializer(typeof(BsonImmutableSerializer<>))]
public class BsonImmutableSerializer<T> : IBsonSerializer<ImmutableArray<T>>
{
    public Type ValueType => typeof(ImmutableArray<T>);

    public object Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        return context.Reader.ReadString().FromJson<ImmutableArray<T>>().ToImmutableArray();
    }

    public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value)
    {
        context.Writer.WriteString(value.ToJson());
    }

    public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, ImmutableArray<T> value)
    {
        context.Writer.WriteString(value.ToJson());
    }

    ImmutableArray<T> IBsonSerializer<ImmutableArray<T>>.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        return context.Reader.ReadString().FromJson<ImmutableArray<T>>().ToImmutableArray();
    }
}

或者

public class ImmutableProvider<T> : IBsonSerializationProvider
{
    public IBsonSerializer GetSerializer(Type type)
    {
        return type == typeof(ImmutableList<T>) ? new ImmutableSerializer<T>() : null;
    }
}

public class ImmutableSerializer<T> : SerializerBase<ImmutableList<T>>
{
    public override ImmutableList<T> Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        return context.Reader.ReadString().FromJson<List<T>>().ToImmutableList();
    }

    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, ImmutableList<T> value)
    {
        context.Writer.WriteString(value.ToJson());
    }
}

第一个解决方案抛出此错误：

系统运行时。序列化。SerializationException:类型为“System”。收藏。不变的ImmutableArray`1[[System.Int32，mscorlib，Version=4.0.0.0，Culture=neutral，PublicKeyToken=b77a5c561934e089]]，数据协定名称为'ArrayFint:http://schemas.microsoft.com/2003/10/Serialization/Arrays”他说。如果您正在使用DATACONTROTSCORALIZER或将未知类型的任何类型添加到已知类型的列表中，请考虑使用DATACONTracTracver，例如，使用NoNyType属性或将它们添加到传递给序列化程序的已知类型的列表中。

第二个投掷：

系统。[0]，'System.收藏。不可变。ImmutableArray1[System.Int32]'， on'MongoDB. Bson.连载。序列化。2[TValue， TIHT]'违反了类型'TValue'的约束。---




Answer 1

通常，您将实现EnumerableSerializerBase

using MongoDB.Bson;
using MongoDB.Bson.IO;
using MongoDB.Bson.Serialization;
using MongoDB.Bson.Serialization.Serializers;
using System;
using System.Collections.Generic;

public abstract class ValueEnumerableSerializerBase<TValue, TItem> : SerializerBase<TValue>, IBsonArraySerializer, IBsonSerializer
    where TValue : struct, IEnumerable<TItem>
{
    private readonly Lazy<IBsonSerializer<TItem>> _lazyItemSerializer;

    protected ValueEnumerableSerializerBase()
        : this(BsonSerializer.SerializerRegistry)
    {
    }

    protected ValueEnumerableSerializerBase(IBsonSerializer<TItem> itemSerializer)
    {
        if (itemSerializer == null)
            throw new ArgumentNullException(nameof(itemSerializer));

        _lazyItemSerializer = new Lazy<IBsonSerializer<TItem>>(() => itemSerializer);
    }

    protected ValueEnumerableSerializerBase(IBsonSerializerRegistry serializerRegistry)
    {
        if (serializerRegistry == null)
            throw new ArgumentNullException(nameof(serializerRegistry));

        _lazyItemSerializer = new Lazy<IBsonSerializer<TItem>>(() => serializerRegistry.GetSerializer<TItem>());
    }

    public IBsonSerializer<TItem> ItemSerializer => _lazyItemSerializer.Value;

    public override TValue Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
    {
        if (context == null)
            throw new ArgumentNullException(nameof(context));

        IBsonReader reader = context.Reader;

        BsonType currentBsonType = reader.GetCurrentBsonType();
        switch (currentBsonType)
        {
            case BsonType.Null:
            {
                reader.ReadNull();
                return default;
            }
            case BsonType.Array:
            {
                reader.ReadStartArray();
                object accumulator = CreateAccumulator();
                while (reader.ReadBsonType() != BsonType.EndOfDocument)
                {
                    TItem item = _lazyItemSerializer.Value.Deserialize(context);
                    AddItem(accumulator, item);
                }
                reader.ReadEndArray();
                return FinalizeResult(accumulator);
            }
            default:
            {
                throw CreateCannotDeserializeFromBsonTypeException(currentBsonType);
            }
        }
    }

    public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, TValue value)
    {
        if (context == null)
            throw new ArgumentNullException(nameof(context));

        IBsonWriter writer = context.Writer;

        if (value.Equals(default))
        {
            writer.WriteNull();
        }
        else
        {
            writer.WriteStartArray();
            foreach (TItem item in EnumerateItemsInSerializationOrder(value))
                _lazyItemSerializer.Value.Serialize(context, item);
            writer.WriteEndArray();
        }
    }

    public bool TryGetItemSerializationInfo(out BsonSerializationInfo serializationInfo)
    {
        IBsonSerializer<TItem> itemSerializer = _lazyItemSerializer.Value;
        serializationInfo = new BsonSerializationInfo(null, itemSerializer, itemSerializer.ValueType);
        return true;
    }

    protected abstract void AddItem(object accumulator, TItem item);

    protected abstract object CreateAccumulator();

    protected abstract IEnumerable<TItem> EnumerateItemsInSerializationOrder(TValue value);

    protected abstract TValue FinalizeResult(object accumulator);
}

从这里开始，ImmutableArray的实现

using MongoDB.Bson.Serialization;
using System.Collections.Generic;
using System.Collections.Immutable;

public class ImmutableArraySerializer<T> : ValueEnumerableSerializerBase<ImmutableArray<T>, T>, IChildSerializerConfigurable
{
    public ImmutableArraySerializer()
    {
    }

    public ImmutableArraySerializer(IBsonSerializer<T> itemSerializer)
        : base(itemSerializer)
    {
    }

    public ImmutableArraySerializer(IBsonSerializerRegistry serializerRegistry)
        : base(serializerRegistry)
    {
    }

    public IBsonSerializer WithItemSerializer(IBsonSerializer<T> itemSerializer)
    {
        return new ImmutableArraySerializer<T>(itemSerializer);
    }

    protected override void AddItem(object accumulator, T item)
    {
        ((ImmutableArray<T>.Builder)accumulator).Add(item);
    }

    protected override object CreateAccumulator()
    {
        return ImmutableArray.CreateBuilder<T>();
    }

    protected override IEnumerable<T> EnumerateItemsInSerializationOrder(ImmutableArray<T> value)
    {
        return value;
    }

    protected override ImmutableArray<T> FinalizeResult(object accumulator)
    {
        return ((ImmutableArray<T>.Builder)accumulator).ToImmutable();
    }

    IBsonSerializer IChildSerializerConfigurable.ChildSerializer => ItemSerializer;

    IBsonSerializer IChildSerializerConfigurable.WithChildSerializer(IBsonSerializer childSerializer)
    {
        return new ImmutableArraySerializer<T>((IBsonSerializer<T>)childSerializer);
    }
}