如何使用json.net自定义反序列化为对象 [英] How to custom deserialize into an object with json.net

问题描述

我使用 http://json2csharp.com/生成了一个代表我的JSON的csharp类，该类工作了太好了.但是，在使用第三方api一段时间后，我意识到他们的响应并不总是发送相同类型的数据.我正在查询其票证数据的API，并且每个票证都有一个SellPrice.有时他们将SellPrice作为具有货币(字符串)和金额(双精度)的Money对象返回，有时将它们作为双精度发送回去.因此，我试图找到一种优雅地处理此问题的方法，以便始终设置我的SellPrice对象的Amount.这是当他们发送Money对象作为SellPrice时工作的代码的简短版本

I used http://json2csharp.com/ to generate a csharp class that represents my JSON, which worked wonderfully. However, after working with the third party api for a while, I realized that their responses aren't always sending the same type of data. I'm querying their API for Ticket data, and each ticket has a SellPrice. Sometimes they return that SellPrice as a Money object that has a currency (string) and amount (double), and sometimes they send it back as just a double. So I'm trying to find a way to handle this gracefully, so that I always set the Amount of my SellPrice object. Here's a short version of the code that works when they send a Money object as SellPrice

public class Ticket
{
    public string Ticket_Id {get; set;}
    //... other fields
    public SellPrice SellPrice {get; set;}
}
public class SellPrice
{
    public string Currency {get; set;}
    public double Amount {get; set;}
}

然后当我得到Json时，我会像这样反序列化，效果很好...

And then when I get the Json, I deserialize like so, which works great...

for (int i = 0; i < jItems.Count; i++)
{
    TUTicket2 item = jItems[i].ToObject<TUTicket2>();
}

...直到我遇到一个API调用，该调用返回一个double而不是一个对象.

...until I run into an API call that returns a double instead of an object.

因此，仅查看Money对象的情况，我认为我会尝试创建一个构造函数，以便可以根据对象类型设置值，如下所示:

So just looking at the case where it's Money object, I thought I'd try to create a constructor so that I can set the values depending on the object type, like so:

public class SellPrice
{
    public SellPrice(object sellPrice)
    {
        if (sellPrice.GetType() == typeof(Dictionary<string, object>))
        {
            Currency = (string)((Dictionary<string, object>)sellPrice)["Currency"];
            Amount = (double)((Dictionary<string, object>)sellPrice)["Currency"];
        }
    }
    public string Currency { get; set; }
    public double Amount { get; set; }
}

但是这不起作用，因为sellPrice对象始终为null，所以我认为我在那儿树错了树.有没有一种方法可以轻松做到这一点?我认为我的问题是将其自动反序列化为对象类型的方式，但是我一直在查看代码/文档，但没有弄清楚我所缺少的内容.

But that doesn't work because the sellPrice object is always null, so I think I'm barking up the wrong tree there. Is there a way to do this easily? I think my problem is the way it auto-deserializes to an object type, but I've been looking through the code/documentation and haven't figured out what I'm missing.

我在这里有两个目标:我们正在做足够的API工作，我希望能够利用json2csharp之类的工具来生成类.我还想避免对每个类/对象进行手动反序列化，尽管如果这是我唯一的选择，我可以朝这个方向发展，当99％的值正常工作时，感觉就像是过分杀伤力.我也不希望根据我进行的API调用而最终得到每个类的X个不同版本.我正在尝试找到一些解决方案，让我只覆盖一小部分而不是所有内容.任何反馈将不胜感激.

I have a couple goals here: We are doing enough API work that I'd like to be able to utilize a tool like json2csharp to generate the classes. I'd also like to avoid doing manual deserialization for every class/object, although if that's my only option, I can go in that direction, it just feels like overkill when 99% of the values behave normally. I also don't want to end up with X different versions of each of my classes depending on which API call I make. I'm trying to find some solution that just lets me override a small portion instead of everything. Any feedback would be appreciated.

推荐答案

您可以通过创建自定义 JsonConverter 用于您的SellPrice类，如下所示:

You can handle this by making a custom JsonConverter for your SellPrice class like this:

public class SellPriceConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(SellPrice);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        JToken token = JToken.Load(reader);
        SellPrice sellPrice = new SellPrice();
        if (token.Type == JTokenType.Object)
        {
            serializer.Populate(token.CreateReader(), sellPrice);
        }
        else if (token.Type == JTokenType.Float)
        {
            sellPrice.Amount = (double)token;
            // if there is a default currency, set it here, e.g.:
            // sellPrice.Currency = "USD";
        }
        else
        {
            throw new JsonException("Unexpected token type for SellPrice: " + token.Type.ToString());
        }
        return sellPrice;
    }

    public override bool CanWrite
    {
        get { return false; }
    }

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

要使用它，只需要做的就是向SellPrice类中添加一个[JsonConverter]属性，如下所示:

To use it, all you would need to do is add a [JsonConverter] attribute to the SellPrice class like this:

[JsonConverter(typeof(SellPriceConverter))]
public class SellPrice 
{
    ...
}

然后，您可以像平常一样反序列化，它应该可以处理两种情况.

Then you can just deserialize as normal and it should handle both situations.

在此处工作的演示: https://dotnetfiddle.net/qZekyp

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