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问如果JsonConvert.DeserializeObject<List<Object>>小于2个JSON对象，则ApiResponse获得异常
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Stack Overflow用户

提问于 2020-11-14 23:52:44

回答 1查看 280关注 0票数 0

我正在尝试将JSON字符串转换为object。

我的模型课：

public class ResponseData<obj> where obj : class
{
    public string message { get; set; }
    public Boolean isSuccess { get; set; }
    public  obj data{ get; set; }
}

public class Registration
{
    public int id { get; set; }
    public int eventId { get; set; }
    public string eventTitle { get; set; }
    public string startDate { get; set; }
    public string status { get; set; }
}

JSON弦

{
  "message": "Success",
  "isSuccess": true,
  "data": [
    {
      "id": 6,
      "eventId": 1,
      "eventTitle": "Test Event",
      "startDate": "2020-10-10T00:00:00",
      "status": "Pending"
    },
    {
      "id": 1,
      "eventId": 4,
      "eventTitle": "dung test",
      "startDate": "2020-10-15T00:00:00",
      "status": "Denied"
    }
  ]
}

我的JsonConvert代码

ResponseData<IList<Registration>> responseListRegistration = JsonConvert.DeserializeObject<ResponseData<IList<Registration>>>(apiResponse);

Problem：只要JSON "data“有多个对象，我的代码就能正常运行。当“数据”只有一个对象时，它会遇到异常。问题是“数据”可能有一个以上的对象。

'System.Collections.Generic.IList`1APT_Admin.Models.Registration‘：无法将当前

对象(例如，{“名称”：“值”})反序列化为类型JsonSerializationException，因为该类型需要一个JSON数组(例如，1,2,3)才能正确地反序列化。要修复此错误，要么将JSON更改为JSON数组(例如，1,2,3)，要么更改反序列化类型，使之成为可以从JSON对象反序列化的普通.NET类型(例如，不像整数这样的原始类型，而不是数组或列表之类的集合类型)。还可以将JsonObjectAttribute添加到类型中，以强制它从JSON对象反序列化。路径'data.id'，第1行，位置51。

我试过：List，IList，IEnumerable，但都一样。

1对象JSON

{
  "message": "Success",
  "isSuccess": true,
  "data": {
    "id": 6,
    "eventId": 1,
    "eventTitle": "Test Event",
    "startDate": "2020-10-10T00:00:00",
    "status": "Pending"
  }
}

谢谢你的阅读

json

回答 1

Stack Overflow用户

发布于 2020-11-15 01:02:00

要在一个类模型中反序列化两个不同的json结构，您需要使用自定义JsonConverter。JsonReader允许您读取第一个令牌。如果是[，则需要反序列化为list。如果它是一个{，一个对象。

void Main()
{
    var json = "{ \"message\": \"Success\", \"isSuccess\": true, \"data\": [ { \"id\": 6, \"eventId\": 1, \"eventTitle\": \"Test Event\", \"startDate\": \"2020-10-10T00:00:00\", \"status\": \"Pending\" }, { \"id\": 1, \"eventId\": 4, \"eventTitle\": \"dung test\", \"startDate\": \"2020-10-15T00:00:00\", \"status\": \"Denied\" } ]}";
    var json2 = "{ \"message\": \"Success\", \"isSuccess\": true, \"data\": { \"id\": 6, \"eventId\": 1, \"eventTitle\": \"Test Event\", \"startDate\": \"2020-10-10T00:00:00\", \"status\": \"Pending\" }}";

    var multiItems = JsonConvert.DeserializeObject<ResponseData<IList<Registration>>>(json);
    var singleItem = JsonConvert.DeserializeObject<ResponseData<IList<Registration>>>(json2);
}

public class ResponseData<T> where T : class
{
    public string message { get; set; }
    public Boolean isSuccess { get; set; }

    [JsonConverterAttribute(typeof(ItemOrListConverter))]
    public T data { get; set; }
}
public class Registration
{
    public int id { get; set; }
    public int eventId { get; set; }
    public string eventTitle { get; set; }
    public string startDate { get; set; }
    public string status { get; set; }
}

public class ItemOrListConverter : Newtonsoft.Json.JsonConverter
{
    public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
    {
        var itemType = objectType.GetGenericArguments()[0];
        var listType = typeof(List<>).MakeGenericType(itemType);

        var result = Activator.CreateInstance(listType) as IList;

        if (reader.TokenType == JsonToken.StartObject)
        {
            var singleObject = serializer.Deserialize(reader, itemType);
            result.Add(singleObject);
        }
        else if (reader.TokenType == JsonToken.StartArray)
        {
            while (reader.Read())
            {
                if (reader.TokenType == JsonToken.EndArray)
                    break;

                var singleObject = serializer.Deserialize(reader, itemType);
                result.Add(singleObject);
            }
        }

        return result;
    }

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

    public override bool CanConvert(Type objectType)
    {
        throw new NotImplementedException();
    }
}

System.Text.Json

void Main()
{
    var json = "{ \"message\": \"Success\", \"isSuccess\": true, \"data\": [ { \"id\": 6, \"eventId\": 1, \"eventTitle\": \"Test Event\", \"startDate\": \"2020-10-10T00:00:00\", \"status\": \"Pending\" }, { \"id\": 1, \"eventId\": 4, \"eventTitle\": \"dung test\", \"startDate\": \"2020-10-15T00:00:00\", \"status\": \"Denied\" } ]}";
    var json2 = "{ \"message\": \"Success\", \"isSuccess\": true, \"data\": { \"id\": 6, \"eventId\": 1, \"eventTitle\": \"Test Event\", \"startDate\": \"2020-10-10T00:00:00\", \"status\": \"Pending\" }}";

    JsonSerializer.Deserialize<ResponseData<IList<Registration>>>(json).Dump();
    JsonSerializer.Deserialize<ResponseData<IList<Registration>>>(json2).Dump();
}

public class ResponseData<T> where T : class
{
    public string message { get; set; }
    public Boolean isSuccess { get; set; }

    [JsonConverterAttribute(typeof(ItemOrListConverterFactory))]
    public T data { get; set; }
}
public class Registration
{
    public int id { get; set; }
    public int eventId { get; set; }
    public string eventTitle { get; set; }
    public string startDate { get; set; }
    public string status { get; set; }
}

public class ItemOrListConverterFactory : JsonConverterFactory
{
    public override bool CanConvert(Type typeToConvert)
        => typeToConvert
            .GetInterfaces()
            .Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEnumerable<>));

    public override System.Text.Json.Serialization.JsonConverter? CreateConverter(Type typeToConvert, JsonSerializerOptions options)
    {
        var itemType = typeToConvert
            .GetInterfaces()
            .First(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IEnumerable<>))
            .GetGenericArguments()[0];

        if (typeToConvert.IsInterface)
        {
            typeToConvert = typeof(List<>).MakeGenericType(itemType);
        }

        return (JsonConverter)Activator.CreateInstance(
            typeof(ItemOrListConverter<>).MakeGenericType(typeToConvert),
            args: new object[] { itemType });
    }
}

public class ItemOrListConverter<T> : JsonConverter<T>
{
    private readonly Type _itemType;

    public ItemOrListConverter(Type itemType)
    {
        _itemType = itemType;
    }

    public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        var result = (IList)Activator.CreateInstance(typeToConvert);

        if (reader.TokenType == JsonTokenType.StartObject)
        {
            var singleObject = JsonSerializer.Deserialize(ref reader, _itemType, options);
            result.Add(singleObject);
        }
        else if (reader.TokenType == JsonTokenType.StartArray)
        {
            while (reader.Read())
            {
                if (reader.TokenType == JsonTokenType.EndArray)
                    break;
                var singleObject = JsonSerializer.Deserialize(ref reader, _itemType, options);
                result.Add(singleObject);
            }
        }

        return (T)result;
    }

    public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }
}

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页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/64839867

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