如何使用 Json.NET 序列化和反序列化数组的 ArrayList

我需要在应用程序中使用 JSON.NET 将对象序列化/反序列化为 json。 Object 具有 ArrayList 属性类型，其中包含字符串数组。为了模拟它，我编写了以下单元测试；

public class JsonTests
{
    public class MyTestClass
    {
        public ArrayList Items { get; private set; }

        public MyTestClass()
        {
            this.Items = new ArrayList();
        }
    }
    [Fact]
    public void JsonConvert_Should_Serialize_ArrayList_And_Deserialize_Successfully()
    {
        MyTestClass myObject = new MyTestClass();
        myObject.Items.Add(new string[] { "Test1", "Test2" });
        string jsonResult = JsonConvert.SerializeObject(myObject);            
        MyTestClass tempMyObject = JsonConvert.DeserializeObject<MyTestClass>(jsonResult);
         //(tempMyObject.Items[0] as string[]) casts to null therefore it throws exception
        Assert.Equal((myObject.Items[0] as string[])[0], (tempMyObject.Items[0] as string[])[0]);
    } 
}

它在序列化过程中不会抛出任何异常。但是，它无法正确反序列化 ArrayList。

我的问题是，如何将其反序列化回字符串数组的 ArrayList ？

Update：另外，我无法更改类定义。该类是在我无法编辑该类的程序集中实现的。

ArrayList是一个非泛型、无类型的集合，因此您需要告知 Json.NET 项目的预期类型。一种方法是使用custom JsonConverter为了ArrayList:

public class ArrayListConverter<TItem> : JsonConverter
{
    public override bool CanWrite { get { return false; } }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;
        var list = serializer.Deserialize<List<TItem>>(reader);
        var arrayList = existingValue as ArrayList ?? new ArrayList(list.Count);
        arrayList.AddRange(list);
        return arrayList;
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(ArrayList);
    }
}

然后将转换器应用到该类，如下所示：

public class MyTestClass
{
    [JsonConverter(typeof(ArrayListConverter<string []>))]
    public ArrayList Items { get; private set; }

    public MyTestClass()
    {
        this.Items = new ArrayList();
    }
}

Sample fiddle.

如果类无法修改，并且您想要所有实例 of ArrayList在您的对象图中将其项目反序列化为string []，您可以将转换器添加到JsonSerializerSettings.Converters而不是将其添加到类型中：

var tempMyObject = JsonConvert.DeserializeObject<MyTestClass>(jsonResult,
                                                              new JsonSerializerSettings { Converters = { new ArrayListConverter<string []>() } });

Sample 小提琴#2.

最后，如果类无法修改并且您只想要特定的ArrayList Items里面的财产MyTestClass将其项目反序列化为string []，您将需要创建一个自定义转换器MyTestClass。您可以使用以下模式自定义反序列化器仅适用于 json.NET 的某些字段自定义反序列化ArrayList属性，同时使用默认反序列化填充其余部分：

public class MyTestClassConverter : JsonConverter
{
    public override bool CanWrite { get { return false; } }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;
        var root = existingValue as MyTestClass ?? (MyTestClass)serializer.ContractResolver.ResolveContract(objectType).DefaultCreator();
        var jsonObject = JObject.Load(reader);

        var jsonItems = jsonObject["Items"].RemoveFromLowestPossibleParent();
        if (jsonItems != null && jsonItems.Type != JTokenType.Null)
        {
            root.Items.AddRange(jsonItems.ToObject<List<string []>>());
        }
        // Populate the remaining standard properties
        using (var subReader = jsonObject.CreateReader())
        {
            serializer.Populate(subReader, root);
        }
        return root;
    }

    public override bool CanConvert(Type objectType)
    {
        return typeof(MyTestClass).IsAssignableFrom(objectType);
    }
}

public static class JsonExtensions
{
    public static JToken RemoveFromLowestPossibleParent(this JToken node)
    {
        if (node == null)
            return null;
        var contained = node.AncestorsAndSelf().Where(t => t.Parent is JContainer && t.Parent.Type != JTokenType.Property).FirstOrDefault();
        if (contained != null)
            contained.Remove();
        // Also detach the node from its immediate containing property -- Remove() does not do this even though it seems like it should
        if (node.Parent is JProperty)
            ((JProperty)node.Parent).Value = null;
        return node;
    }
}

然后按如下方式使用它：

var tempMyObject = JsonConvert.DeserializeObject<MyTestClass>(jsonResult,
                                                              new JsonSerializerSettings { Converters = { new MyTestClassConverter() } });

Sample 小提琴#3.