在C#代码中读取JSON文件时遇到问题

Question

我在读取一个特定的JSON文件时遇到了一些问题。我的代码正在读取其他JSON文件，所以我猜我正在做一些非常愚蠢的事情，但我已经盯着它看了大约一个小时，但没有成功。我有以下代码

        List<VFData> visualFieldData;


        public class VFData
        {
            public double x { get; set; }
            public double y { get; set; }
            public string type { get; set; }
            public double contrast { get; set; }
        }

        private void LoadVFDataJSONFile(string VFdataFile )
        {
            string jsonStream;
            using (StreamReader r = new StreamReader(VFdataFile))
            {
                jsonStream = r.ReadToEnd();
            }
            visualFieldData = JsonConvert.DeserializeObject<List<VFData>>(jsonStream);
        }


The JSON file has the following format


[
  {
    "x": -4.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.670277655
  },
  {
    "x": -14.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.407872766
  },
  {
    "x": -24.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.372877628
  },
  {
    "x": -34.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.4652638
  },
  {
    "x": -4.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.399946272
  },
  {
    "x": -4.0,
    "y": 24.0,
    "type": "vf",
    "contrast": 0.420959234
  },
  {
    "x": -14.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.3694598
  },
  {
    "x": -14.0,
    "y": 24.0,
    "type": "vf",
    "contrast": 0.4507869
  },
  {
    "x": -24.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.4334121
  },
  {
    "x": 4.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.515925348
  },
  {
    "x": 14.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.487090856
  },
  {
    "x": 24.0,
    "y": 4.0,
    "type": "vf",
    "contrast": 0.5159793
  },
  {
    "x": 4.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.3921606
  },
  {
    "x": 4.0,
    "y": 24.0,
    "type": "vf",
    "contrast": 0.4164949
  },
  {
    "x": 14.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.392385662
  },
  {
    "x": 14.0,
    "y": 24.0,
    "type": "vf",
    "contrast": 0.426395863
  },
  {
    "x": 24.0,
    "y": 14.0,
    "type": "vf",
    "contrast": 0.4305214
  },
  {
    "x": 4.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.377473235
  },
  {
    "x": 14.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.355986029
  },
  {
    "x": 24.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.3789097
  },
  {
    "x": 4.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.396197081
  },
  {
    "x": 4.0,
    "y": -24.0,
    "type": "vf",
    "contrast": 0.363053441
  },
  {
    "x": 14.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.384389132
  },
  {
    "x": 14.0,
    "y": -24.0,
    "type": "vf",
    "contrast": 0.440146685
  },
  {
    "x": 24.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.387488931
  },
  {
    "x": -4.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.366485029
  },
  {
    "x": -14.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.392450541
  },
  {
    "x": -24.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.428462267
  },
  {
    "x": -34.0,
    "y": -4.0,
    "type": "vf",
    "contrast": 0.394372374
  },
  {
    "x": -4.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.377464861
  },
  {
    "x": -4.0,
    "y": -24.0,
    "type": "vf",
    "contrast": 0.372114331
  },
  {
    "x": -14.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.377241641
  },
  {
    "x": -14.0,
    "y": -24.0,
    "type": "vf",
    "contrast": 0.42327565
  },
  {
    "x": -24.0,
    "y": -14.0,
    "type": "vf",
    "contrast": 0.407872945
  }
]

我得到以下错误

'System.Collections.Generic.List`1WindowsFormsApp1.Form1+VFData‘：’无法将当前JSON对象(例如，{“名称”：“值”})反序列化为类型Newtonsoft.Json.JsonSerializationException，因为该类型需要一个JSON数组(例如，1、2、3)才能正确反序列化。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'x'，第1行，位置5‘

Answer 1

总是检验你的假设

var jsonData = @"[
  {
    ""x"": -4.0,
    ""y"": 4.0,
    ""type"": ""vf"",
    ""contrast"": 0.670277655
  },
  {
    ""x"": -14.0,
    ""y"": 4.0,
    ""type"": ""vf"",
    ""contrast"": 0.407872766
  },
  {
    ""x"": -24.0,
    ""y"": -14.0,
    ""type"": ""vf"",
    ""contrast"": 0.407872945
  }
]";
var visualFieldData = JsonConvert.DeserializeObject<List<VFData>>(jsonData);

上面的代码运行良好，没有任何例外(我用完整的json示例进行了测试，只是为了得到答案而缩短了它)。我建议在调试模式下运行，查看实际要转换的字符串，或者添加某种日志语句来显示json字符串。

我们无法知道您是否读取了错误的文件，该文件是否已损坏字符，或者是否正在发生其他问题--但我可以肯定的一点是，您问题中的JSON在反序列化类中运行良好

编辑:看看我猜到的错误，下面的代码会产生相同的错误

try
{
    var jsonData = @"
      {
        ""x"": -4.0,
        ""y"": 4.0,
        ""type"": ""vf"",
        ""contrast"": 0.670277655
      }";
    var visualFieldData = JsonConvert.DeserializeObject<List<VFData>>(jsonData);
    }
    catch (Exception ex)
    {
        logger.Info(ex.Message);
        logger.Info(ex.StackTrace);
    }
}

它可能是您的文件有一个项目，而不是一个项目数组。解决方案只是反序列化到VFData的单个实例，而不是列表。

var visualFieldData = JsonConvert.DeserializeObject<VFData>(jsonData);