• Similar to the previous section
• We can parse a JSON string into an array
• Simply replace the original class name with List<ClassName>

Example

string jsonString = @"""{""webinfos"":[{""webname"":""FoxDevelop"",""website"":""foxdevelop.com"",""age"":4,
""students"":[{""name"":""Oliver""},{""name"":""Noah""}]},{""webname"":""FoxDevelop1"",""website"":""foxdevelop.com1"",
""age"":6,""students"":[{""name"":""Liam""},{""name"":""Ethan""}]}]}""";

StringReader sr = new StringReader(jsonString);
JsonReader jr = new JsonReader(sr);
List<WebInfo> infoList = new JsonSerializer().Deserialize(jr, typeof(List<WebInfo>)) as List<WebInfo>;

Notes

1. Keep code structure, variable names, escaped double‑quotes and line breaks unchanged, only replace target text
2. Do not modify subsequent deserialization logic

① Serialize List to JSON array string

// Construct List collection
List<WebInfo> webList = new List<WebInfo>()
{
    new WebInfo()
    {
        age = 4,
        webname = "FoxDevelop",
        website = "foxdevelop.com",
        students = new Person[] { new Person{name="Oliver"}, new Person{name="Noah"} }
    },
    new WebInfo()
    {
        age = 4,
        webname = "FoxDevelop1",
        website = "foxdevelop.com",
        students = new Person[] { new Person{name="Liam"}, new Person{name="Ethan"} }
    },
    new WebInfo()
    {
        age = 4,
        webname = "FoxDevelop2",
        website = "foxdevelop.com",
        students = new Person[] { new Person{name="Mason"}, new Person{name="Logan"} }
    }
};

// Serialize: List object → JSON‑array string
StringWriter sw = new StringWriter();
JsonWriter writer = new JsonWriter(sw);
new JsonSerializer().Serialize(writer, webList);
string jsonArrStr = sw.GetStringBuilder().ToString();

② Deserialize JSON‑array string to List

string jsonString = @"[{"webname":"FoxDevelop","website":"foxdevelop.com","age":4,
"students":[{"name":"Oliver"},{"name":"Noah"}]},{"webname":"FoxDevelop1","website":"foxdevelop.com",
"age":4,"students":[{"name":"Liam"},{"name":"Ethan"}]},{"webname":"FoxDevelop2","website":"foxdevelop.com",
"age":4,"students":[{"name":"Mason"},{"name":"Logan"}]}]";

StringReader sr = new StringReader(jsonString);
JsonReader jr = new JsonTextReader(sr);
List<WebInfo> dataList = new JsonSerializer().Deserialize(jr, typeof(List<WebInfo>)) as List<WebInfo>;

Array serialization and deserialization

Let’s recap serialization from the previous section, which converts an entity object into a JSON string.

Serialization

WebInfo webInfo = new WebInfo();
webInfo.age = 4;
webInfo.webname = "FoxDevelop";
webInfo.website = "foxdevelop.com";
webInfo.students = new Person[] { new Person { name = "Tom" }, new Person { name = "Jim" } };
// Convert the webinfo object to a JSON string
StringWriter sw = new StringWriter();
JsonWriter writer = new JsonWriter(sw);
new JsonSerializer().Serialize(writer, webInfo);
string json = sw.GetStringBuilder().ToString();

Generated JSON output

{"webname":"FoxDevelop","website":"foxdevelop.com","age":4,"students":[{"name":"Zhang San"},{"name":"Li Si"}]}

Deserialization

Convert a JSON string back to an entity object

Method 1 (low‑level Reader approach)

WebInfo model = new JsonSerializer()
    .Deserialize(new JsonTextReader(new StringReader(json)), typeof(WebInfo)) as WebInfo;

Method 2 (concise generic syntax, Newtonsoft.Json)

WebInfo model = JavaScriptConvert.DeserializeObject<WebInfo>(json);

new JsonSerializer().Deserialize(new JsonTextReader(new StringReader(jsonString)), typeof(ClassName) as ClassName

With the above methods, we can deserialize JSON into entity objects.

Alternative usage

JavaScriptConvert.DeserializeObject<NodeInfo>(jsonText)

Serialization and deserialization

Newtonsoft.Json (commonly known as Json.NET) is an open‑source JSON serialization/deserialization library for the .NET ecosystem

• First release Json.NET 1.0.1 launched in 2006, major versions have reached 10+
• Originally compatible with .NET 2.0, supports nearly all .NET frameworks (Framework/.NET Core/.NET 5+)
• Assembly: Newtonsoft.Json.dll, install via NuGet
• Source code was hosted on CodePlex in early days, now migrated to GitHub, widely adopted in enterprise‑level projects

2. What is JSON

JSON（JavaScript Object Notation）

• Lightweight, language‑agnostic text‑based data‑exchange format, not exclusive to JavaScript
• Core structure: key‑value pair key:value; supports nested objects {} and arrays []

{"webname":"FoxDevelop","website":"foxdevelop.com","age":4,"students":[{"name":"tom"},{"name":"bill"}]}

II. Define Entity Classes (Map to JSON Structure)

Person.cs (Student Object)

namespace NewtonsoftDemo
{
    public class Person
    {
        public string name { set; get; }
    }
}

WebInfo.cs (Root Object)

namespace NewtonsoftDemo
{
    public class WebInfo
    {
        public string webname { set; get; }
        public string website { set; get; }
        public int age { set; get; }
        public Person[] students { set; get; }
    }
}

Example‑Serialize Object to JSON

protected void Page_Load(object sender, EventArgs e)
{
    // 1. Instantiate entity and assign values
    WebInfo webInfo = new WebInfo();
    webInfo.age = 4;
    webInfo.webname = "FoxDevelop";
    webInfo.website = "foxdevelop.com";
    webInfo.students = new Person[] 
    { 
        new Person { name = "TOM" },
        new Person { name = "JACK" } 
    };

    // 2. Low‑level Newtonsoft.Json: serialize with JsonWriter
    StringWriter sw = new StringWriter();
    JsonWriter writer = new JsonWriter(sw);
    new JsonSerializer().Serialize(writer, webInfo);
    string json = sw.GetStringBuilder().ToString();
}

Simplified Code for Daily Use

Newtonsoft.Json provides static helper methods to avoid manually creating JsonWriter:

// One‑line serialization, widely used in development
string json = JsonConvert.SerializeObject(webInfo);

Output JSON Result

{
  "webname": "FoxDevelop",
  "website": "foxdevelop.com",
  "age": "4",
  "students": [
    {"name":"TOM"},
    {"name":"JACK"}
  ]
}

Others

• System.Text.Json: Microsoft built‑in JSON library starting from .NET Core 3.0; Newtonsoft.Json is still popular for legacy .NET Framework projects
• Features: property aliasing, field ignoring, date formatting, circular reference handling and other advanced capabilities

Introduction