c# - .Net5 中 JArray.FromObject() 的等价物？

Question

我们有一个使用 System.Text.Json 的项目在 .NET 5 中而不是 Newtonsoft JObject .使用 Newtonsoft，替换动态 JSON 数据非常容易，例如如下图:

siteDataObject["student"] = JArray.FromObject(studentservice.GetStudents());

当studentservice.GetStudents()返回List时结构如下

internal class Student {
    public int Id { get; set; }
    public string Name { get; set; }
    public string ContactPhone { get; set; }

    public IEnumerable<MedicalRecord> MedicalRecords { get; set; }
}

internal class MedicalRecord {
    public int Id { get; set; }
    public string Name { get; set; }
    public DateTime RecordDate { get; set; }
    public IEnumerable<DiseaseLog> DiseaseLogs{ get; set; }
}

internal class DiseaseLog {
    public int Id { get; set; }
    public string Name { get; set; }
    public DateTime LogDate { get; set; }
}

但在 System.Text.Json 中

foreach (var element in doc.RootElement.EnumerateObject()) {
    if (element.Name == "student") {
        writer.WritePropertyName(element.Name);
    
    }
    else {
        element.WriteTo(writer);
    }
}

我不知道如何转换List<student>转换成 JSON 数组数据，当学生类有很多属性，里面有多个集合。

谁能告诉我如何转换它？

为了澄清，我需要为此提出完整的代码，我有一个动态的 json 字符串并且想将元素:学生替换为新记录，代码将是

var dynamicJson = @"{'roomid':1,'roomcode':'Code001','students':[1],'contentdata':'say hello','footerdata':'cookie policy'}";
using MemoryStream stream = new MemoryStream();
using Utf8JsonWriter writer = new Utf8JsonWriter(stream);
using var dynamicDocument = JsonDocument.Parse(dynamicJson);
writer.WriteStartObject();
foreach (var element in dynamicDocument.RootElement.EnumerateObject())
{
    if (element.Name == "students")
    {
        // unknown how to modify the student record into array
    }
    else
        element.WriteTo(writer);
}
writer.WriteEndObject();
stream.Flush();
var modifyJson = Encoding.UTF8.GetString(stream.ToArray());

如果学生元素是字符串，我知道如何修改学生值，但我不知道如何使用简单代码将其修改为数组。由于学生在里面有多个类(class)。

我的预期结果应该是

{
    "roomid": 1,
    "roomcode": "Code001",
    "students": [
        {
            "id": 1,
            "Name": "Wilson",
            "ContactPhone": "123-122-3311",
            "MedicalRecords": [
                {
                    "id": 101,
                    "Name ": "Medial record 101011",
                    "RecordDate": "2021-12-31",
                    "DiseaseLogs": [
                        {
                            "id": 18211,
                            "Name ": "Patient Log 19292",
                            "LogDate": "2020-1-31"
                        },
                        {
                            "id": 18212,
                            "Name ": "Patient Log 2911w",
                            "LogDate": "2020-3-31"
                        }
                    ]
                }
            ]
        }
    ],
    "contentdata": "say hello",
    "footerdata": "cookie policy"
}

Answer 1

在 .NET 5 中，System.Text.Json 中没有内置可修改的 JSON 文档对象模型。 JsonDocument 是只读的， System.Text.Json.Nodes 仅在 .NET 6 中引入。因此，在 .NET 5 中反序列化、修改和重新序列化自由格式 JSON 的最简单方法是反序列化为某些部分数据模型，将未知值绑定(bind)到字典。

如果您不关心根级别的属性顺序，您可以反序列化为带有 public object students { get; set; } 的模型属性，并将其余元素绑定(bind)到 JsonExtensionData 溢出字典:

public class RootObject
{
    public object students { get; set; }

    [System.Text.Json.Serialization.JsonExtensionDataAttribute]
    public IDictionary<string, object> ExtensionData { get; set; }
}

然后反序列化，修改，重新序列化如下:

var students = new List<Student> { /* Initialize these as required... */ };

var dynamicJson = @"{""roomid"":1,""roomcode"":""Code001"",""students"":[1],""contentdata"":""say hello"",""footerdata"":""cookie policy""}";

var root = JsonSerializer.Deserialize<RootObject>(dynamicJson);

root.students = students;

var modifyJson = JsonSerializer.Serialize(root, new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase, WriteIndented = true });

结果

{
  "students": [
    {
      "id": 1,
      "name": "Wilson",
      "contactPhone": "123-122-3311",
      "medicalRecords": [
        {
          "id": 101,
          "name": "Medial record 101011",
          "recordDate": "2021-12-31T00:00:00",
          "diseaseLogs": [
            {
              "id": 18211,
              "name": "Patient Log 19292",
              "logDate": "2020-01-31T00:00:00"
            },
            {
              "id": 18212,
              "name": "Patient Log 2911w",
              "logDate": "2020-03-31T00:00:00"
            }
          ]
        }
      ]
    }
  ],
  "roomid": 1,
  "roomcode": "Code001",
  "contentdata": "say hello",
  "footerdata": "cookie policy"
}

students属性必须声明为 object因为输入的 JSON 已经有一个包含单个整数值的数组；声明为 public List<Student> students { get; set; }最初加载 JSON 时会导致反序列化。

演示 fiddle #1 here .

如果您确实关心根级别的属性顺序，您可以反序列化为 OrderedDictionary (可追溯到 .NET Framework 2.0 的旧的保序非泛型字典仍然存在并受支持)，覆盖 "students"值，并重新序列化:

var students = new List<Student> { /* Initialize these as required... */ };

var dynamicJson = @"{""roomid"":1,""roomcode"":""Code001"",""students"":[1],""contentdata"":""say hello"",""footerdata"":""cookie policy""}";

var root = JsonSerializer.Deserialize<OrderedDictionary>(dynamicJson);

root["students"] = students;

var modifyJson = JsonSerializer.Serialize(root, new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase, WriteIndented = true });

结果

{
  "roomid": 1,
  "roomcode": "Code001",
  "students": [
    {
      "id": 1,
      "name": "Wilson",
      "contactPhone": "123-122-3311",
      "medicalRecords": [
        {
          "id": 101,
          "name": "Medial record 101011",
          "recordDate": "2021-12-31T00:00:00",
          "diseaseLogs": [
            {
              "id": 18211,
              "name": "Patient Log 19292",
              "logDate": "2020-01-31T00:00:00"
            },
            {
              "id": 18212,
              "name": "Patient Log 2911w",
              "logDate": "2020-03-31T00:00:00"
            }
          ]
        }
      ]
    }
  ],
  "contentdata": "say hello",
  "footerdata": "cookie policy"
}

演示 fiddle #2 here .

---

在 .NET 6 中，这一切都通过使用 System.Text.Json.Nodes 变得更加容易可编辑的 JSON 文档对象模型:

var dynamicJson = @"{""roomid"":1,""roomcode"":""Code001"",""students"":[1],""contentdata"":""say hello"",""footerdata"":""cookie policy""}";

var nodes = JsonSerializer.Deserialize<JsonObject>(dynamicJson);

nodes["students"] = JsonSerializer.SerializeToNode(students, new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase });

var modifyJson = nodes.ToString();

但在 .NET 5 中这是不可能的。演示 fiddle #3 here .