【c#】JSON操作

C#中使用Json，安装Newtonsoft.json依赖

读取json文件

注意：检查json文件的编码类型，是否为UTF-8。不是的话，读取到的中文会乱码

方法：json文件使用记事本打开，界面下方会显示编码类型。若不是，将文件另存为，更改即可。

private JObject ReadJsonFile(string folder, string fileName){
    string filePath = System.IO.Path.Combine(folder + "/" + fileName);
    using (System.IO.StreamReader file = System.IO.File.OpenText(filePath))
    {
        using (JsonTextReader reader = new JsonTextReader(file))
        {
            JObject jObject = (JObject)JToken.ReadFrom(reader);
            return jObject;
        }
    }
}

写入json文件

 private void WriteJsonFile(string folder, string fileName, JObject jObject){
     string filePath = System.IO.Path.Combine(folder + "/" + fileName);
     using (System.IO.StreamWriter file = new System.IO.StreamWriter(filePath))
     {
         file.Write(jObject.ToString());
     }
 }

几种常用类型

JObject 用于操作json对象

JToken 用于存放linq查询的结果

JArray 用于json数组

JValue 表示数组中的值

JProperty 表示对象的属性

JObject jo = new JObject(){{"name","张珊"},{"age",18}};
// {"name":"张三",“age”:18}

JToken jname = jo["Name"];

string[] girlFriends = {"韩梅梅","橘朵"};

JArray ja = new JArray();
foreach(var name in girlFriends){
    ja.Add(new JValue(name));
}

jo.Add(new JProperty("girlFriends",ja));

几种常用API

JObject.Parse 用于将字符串格式转成JObject

jo.ToObject<T> 用于将 JObject 类型转化成 实体类

JObject.FromObject 用于将 实体类 转化成 JObject

LINQ to JSON

查询

JObject o = JObject.Parse(@"{
  'CPU': 'Intel',
  'Drives': [
    'DVD read/writer',
    '500 gigabyte hard drive'
  ]
}");

List<string> allDrives = o["Drives"].Select(t => (string)t).ToList();//["DVD read/writer","500 gigabyte hard drive"]

新建

List<Post> GetPosts()
{
    List<Post> posts = new List<Post>() {
    new Post(){ Title = "A",Description ="A is a",Link = "http://www.a.com",Categories = new List<string>(){ "apple","alpha"} },
    new Post(){ Title = "B",Description ="B is b",Link = "http://www.b.com",Categories = new List<string>(){ "belt","baby"} },
    new Post(){ Title = "C",Description ="C is c",Link = "http://www.c.com",Categories = new List<string>(){ "cut","city"} }
    };
    return posts;
}
List<Post> posts = GetPosts();

JArray itemJArray = new JArray(
    from p in posts
    orderby p.Title
    select new JObject(
        new JProperty("title", p.Title),
        new JProperty("description", p.Description),
        new JProperty("link", p.Link),
        new JProperty("category",
        new JArray(
            from c in p.Categories
            select new JValue(c)
            )
        )
        )
    );

class Post
{
    public string? Title;
    public string? Description;
    public string? Link;
    public List<string>? Categories;
}

对象变JObject

JObject pp = JObject.FromObject(new
{
    channel = new
    {
        title = "D",
        link = "http://www.d.com",
        description = "D is d",
        item =
            from p in posts
            orderby p.Title
            select new
            {
                title = p.Title,
                description = p.Description,
                link = p.Link,
                category = p.Categories
            }
    }
});

path 获取值

pp.SelectToken("channel.item[0].title")

序列化

string aa = JsonConvert.SerializeObject(posts[0]);//对象序列化（变成json格式的字符串）
Post ppp = JsonConvert.DeserializeObject<Post>(aa);//json字符串 反序列化 （变成对象）

string json = @"{""key1"":""value1"",""key2"":""value2""}";
Dictionary<string, string> values = JsonConvert.DeserializeObject<Dictionary<string, string>>(json);