Question

我有一个JSON文件，例如：

{
   "samples":[
      {
         "date":"2014-08-10T09:00:00Z",
         "temperature":10,
         "pH":4,
         "phosphate":4,
         "chloride":4,
         "nitrate":10
      },
      {
         "date":"2014-08-12T09:05:00Z",
         "temperature":10.5,
         "pH":5,
         "chloride":4,
         "phosphate":4
      },
      {
         "date":"2014-08-14T09:02:00Z",
         "temperature":10.8,
         "pH":3,
         "phosphate":4
      },
      {
         "date":"2014-08-16T09:02:00Z",
         "temperature":11.2,
         "pH":6,
         "chloride":4
      },
      {
         "date":"2014-08-18T08:58:00Z",
         "temperature":10.9,
         "pH":10,
         "chloride":4,
         "phosphate":4,
         "nitrate":10
      },
      {
         "date":"2014-08-20T09:10:00Z",
         "temperature":9.3,
         "pH":6,
         "phosphate":4
      },
      {
         "date":"2014-08-22T09:01:00Z",
         "temperature":9.5,
         "pH":10,
         "chloride":4,
         "phosphate":4,
         "nitrate":10
      }
   ]
}

我需要访问每个子元素，例如“温度”，“ pH”等，以计算它们的平均值。为此，我想使用反序列化器。首先，我创建了一个自定义类来保存json的参数，

public class SampleClass
{
    public float temperature { get; set; } = 0;
    public int pH { get; set; } = 0;
    public int phosphate { get; set; } = 0;
    public int chloride { get; set; } = 0;
    public int nitrate { get; set; } = 0;

}

紧接着，我使用此自定义类应用了反序列化器；

List<SampleClass> json = JsonConvert.DeserializeObject<List<SampleClass>>(jsonStr);

使用上面的代码行，我遇到了错误；

Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[GeneralKnowledge.Test.App.Tests.SampleClass]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.
To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List<T>) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.
Path 'samples', line 2, position 14.

您会建议我解决什么问题？预先感谢。

Answer 1

假设您的JSON如下：

{
   "samples":[ ... ]
}

您有一个外部容器对象，该对象封装了样本数组。您需要反序列化为反映此结构的数据模型。一种简单的方法是使用匿名对象以及JsonConvert.DeserializeAnonymousType()：

var result = JsonConvert.DeserializeAnonymousType(jsonStr, new { samples = default(List<SampleClass>) })
    .samples;

这种方法避免将JSON加载到中间的dynamic或JToken表示形式中。

提琴here。

Answer 2

尝试一下：

dynamic json = Newtonsoft.Json.JsonConvert.DeserializeObject(json_string);
List<SampleClass> result = JsonConvert.DeserializeObject<List<SampleClass>>(json.samples.ToString());

但如果没有，请使用此

 List<SampleClass> result = new List<SampleClass>();
 foreach (var item in json.samples)
 {               
  result.Add(Newtonsoft.Json.JsonConvert.DeserializeObject<SampleClass>(item.ToString()));
 }

JSON反序列化不适用于List对象

2 个答案: