c# - Newtonsoft JsonConverter 将字符串或对象转换为对象

Question

我有一些反序列化的要求，我正在尝试处理我可能拥有这些潜在输入的地方:

{
    "value": "a string"
}

-- 或--

{
    "value": {
        "text": "a string"
        // there are other properties, but for successful deserialization I only need text present
    }
}

我希望它能够成功转换为对象MyObject:

public class MyObject
{
    [JsonProperty("text")
    public string Text { get; set; }
}

到目前为止，这就是我的转换器中的内容。这种情况在它是一个字符串时工作正常(虽然不是很有效，因为我抛出异常来捕获失败的反序列化)。但是，当它是一个对象时，读取器会抛出异常，我不确定如何处理它。

public class MyObjectConverter : JsonConverter
{
    public override bool CanWrite { get => false; }

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

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(string) || objectType == typeof(MyObject);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var value = reader.Value?.ToString();
        if (string.IsNullOrWhiteSpace(value))
        {
            return null;
        }

        try
        {
            return JObject.Parse(value).ToObject<MyObject>();
        }
        catch (Exception)
        {
            return new MyObject
            {
                Text = value
            };
        }
    }
}

也许我已经有了一个我不知道的好方法？如果不是，我如何确定我的输入是字符串还是对象，以便能够返回我关心的对象？

解决方案:

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.String)
        {
            return new MyObject
            {
                Text = reader.Value?.ToString()
            };
        }
        else if (reader.TokenType == JsonToken.StartObject)
        {
            JObject obj = JObject.Load(reader);
            return obj.ToObject<MyObject>();
        }
        else
        {
            return null;
        }
    }

Answer 1

您的对象的结构与您期望的输入不同。对于第二种情况，MyObject 需要如下所示:

// this is ugly
public class MyObject
{
    public Value value{get;set;}

    public class Value{
         public string text {get;set;}
    }
}

如果你想像现在一样只拥有一个具有单个 Text 属性的对象，你可以这样做:

public override object ReadJson(JsonReader reader, Type objectType, object 
    existingValue, JsonSerializer serializer)
{
    JObject obj = JObject.Load(reader);
    var value = obj["value"];

    if(value is JObject)  // this will be true if the value property is a nested structure
       return new MyObject(){Text=value["text"]};  // could also do value.ToObject<MyObject>() if you need more properties
    else
       return new MyObject(){Text=value};
}