C# 使用 JSON

C# 文件的输入与输出上一节:C# 文件的输入与输出C# 特性（Attribute）下一节:C# 特性（Attribute）

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C#有两种常见办法可以解析和使用JSON：一是使用.NET Framwork3.5或更高版本自带的System.Runtime.Serialization.Json库。二是使用Newtonsoft提供的JSON解析库。下面分别介绍。

一、使用系统自带库

1、Using

首先，需要添加引用：System.ServiceModel.Web 和 System.Runtime.Serialization，然后使用Using：

using System.Runtime.Serialization.Json;
using System.Runtime.Serialization;

2、定义序列化的类

假如我们要转化的JSON字符串格式为：

{
    "encoding":"UTF-8",
    "plug-ins":["python","c++","ruby"],
    "indent":{
        "length":3,
        "use_space":true
    }
}

然后编写相应的序列化的类，注意下面类加的Attribute：

[DataContract(Namespace = "http://coderzh.cnblogs.com")]
class Config
{
    [DataMember(Order = 0)]
    public string encoding { get; set; }
    [DataMember(Order = 1)]
    public string[] plugins { get; set; }
    [DataMember(Order = 2)]
    public Indent indent { get; set; }
}
 
[DataContract(Namespace = "http://coderzh.cnblogs.com")]
class Indent
{
    [DataMember(Order = 0)]
    public int length { get; set; }
    [DataMember(Order = 1)]
    public bool use_space { get; set; }
}

3、对象转化为JSON字符串

使用WriteObject方法：

var config = new Config(){
                         encoding = "UTF-8",
                         plugins = new string[]{"python", "C++", "C#"},
                         indent = new Indent(){ length = 4, use_space = false}
                         };
var serializer = new DataContractJsonSerializer(typeof(Config));
var stream = new MemoryStream();
serializer.WriteObject(stream, config);
byte[] dataBytes = new byte[stream.Length];
stream.Position = 0;
stream.Read(dataBytes, 0, (int)stream.Length);
string dataString = Encoding.UTF8.GetString(dataBytes);
Console.WriteLine("JSON string is:");
Console.WriteLine(dataString);

4、JSON字符串转对象

使用ReadObject方法：

var mStream = new MemoryStream(Encoding.Default.GetBytes(dataString));
Config readConfig = (Config)serializer.ReadObject(mStream);
 
Console.WriteLine("Encoding is: {0}", readConfig.encoding);
foreach (string plugin in readConfig.plugins)
{
    Console.WriteLine("plugins is: {0}", plugin);
}
Console.WriteLine("indent.length is: {0}", readConfig.indent.length);
Console.WriteLine("indent.use_space is: {0}", readConfig.indent.use_space);

5、输出结果：

JSON string is:
{"encoding":"UTF-8","plugins":["python","C++","C#"],"indent":{"length":4,"use_space":false}}
Encoding is: UTF-8
plugins is: python
plugins is: C++
plugins is: C#
indent.length is: 4
indent.use_space is: False

二、Newtonsoft提供的Json.dll

这是一个Newtonsoft提供的第三方库，需要下载并引用dll:Newtonsoft.Json.dll。官方下载地址： http://www.newtonsoft.com/

使用示例如下：

//读取简单的json
string json="{\"username\":\"张三\"}";
string username = string.Empty;
JObject jObj=JObject.Parse(json); //进行格式化
username = jObj["username"].ToString();
Console.WriteLine(username);
 
//读取嵌套对象的json
json = "{\"username\":\"张三\",data:{\"address\":\"福建厦门\"}}";
jObj = JObject.Parse(json);
string address = string.Empty;
address = jObj["data"]["address"].ToString();
Console.WriteLine(address);
 
//读取数组,操作方式与数组类似
json = "{\"username\":\"张三\",data:[{\"address\":\"福建厦门\"},{\"address\":\"福建福州\"}]}";
jObj = JObject.Parse(json);
 address = string.Empty;
address = jObj["data"][0]["address"].ToString()+","+ jObj["data"][1]["address"].ToString();
Console.WriteLine(address);
 
Console.ReadLine();

C# 文件的输入与输出上一节:C# 文件的输入与输出C# 特性（Attribute）下一节:C# 特性（Attribute）

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