核心功能

1. 基础序列化/反序列化

• JsonConvert.SerializeObject() – 对象转JSON
• JsonConvert.DeserializeObject<T>() – JSON转对象

2. 属性控制

• [JsonProperty] – 自定义属性名
• [JsonIgnore] – 忽略属性
• [JsonConverter] – 自定义转换器

3. 格式化选项

• Formatting.Indented – 格式化输出
• NullValueHandling – 空值处理
• DefaultValueHandling – 默认值处理

4. 动态操作

• JObject – 动态创建和修改JSON
• JArray – JSON数组操作
• LINQ to JSON – 使用LINQ查询JSON

5. 高级特性

• 自定义JsonConverter
• 错误处理机制
• 性能优化设置
• 驼峰命名转换

using System;
using System.Collections.Generic;
using System.Linq;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Newtonsoft.Json.Linq;
using Newtonsoft.Json.Serialization;

// 1. 基本模型定义
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
    public string Email { get; set; }
    public DateTime BirthDate { get; set; }
    public List<string> Hobbies { get; set; } = new List<string>();
}

// 2. 带属性配置的复杂模型
public class Product
{
    [JsonProperty("product_id")]
    public int Id { get; set; }
    
    [JsonProperty("product_name")]
    public string Name { get; set; }
    
    [JsonProperty("unit_price")]
    public decimal Price { get; set; }
    
    [JsonProperty("created_date")]
    [JsonConverter(typeof(IsoDateTimeConverter))]
    public DateTime CreatedDate { get; set; }
    
    [JsonProperty("is_active")]
    public bool IsActive { get; set; }
    
    // 忽略序列化
    [JsonIgnore]
    public string InternalNotes { get; set; }
    
    // 条件序列化
    [JsonProperty("description")]
    public string Description { get; set; }
    
    public bool ShouldSerializeDescription()
    {
        return !string.IsNullOrEmpty(Description);
    }
}

// 3. 嵌套对象模型
public class Order
{
    public int OrderId { get; set; }
    public Person Customer { get; set; }
    public List<OrderItem> Items { get; set; } = new List<OrderItem>();
    public decimal TotalAmount { get; set; }
    public OrderStatus Status { get; set; }
}

public class OrderItem
{
    public Product Product { get; set; }
    public int Quantity { get; set; }
    public decimal UnitPrice { get; set; }
}

public enum OrderStatus
{
    Pending,
    Processing,
    Shipped,
    Delivered,
    Cancelled
}

public class NewtonsoftJsonExamples
{
    public static void RunAllExamples()
    {
        Console.WriteLine("=== Newtonsoft.Json 使用案例 ===\n");
        
        BasicSerializationExample();
        BasicDeserializationExample();
        JsonPropertyAttributeExample();
        JsonIgnoreExample();
        DateTimeHandlingExample();
        EnumHandlingExample();
        CustomSerializationExample();
        JObjectDynamicExample();
        LinqToJsonExample();
        ErrorHandlingExample();
        PerformanceOptimizationExample();
        JsonConverterExample();
        NullValueHandlingExample();
        CamelCaseExample();
    }
    
    // 1. 基础序列化
    public static void BasicSerializationExample()
    {
        Console.WriteLine("1. 基础序列化示例:");
        
        var person = new Person
        {
            Name = "张三",
            Age = 30,
            Email = "zhangsan@example.com",
            BirthDate = new DateTime(1993, 5, 15),
            Hobbies = new List<string> { "阅读", "游泳", "编程" }
        };
        
        // 基本序列化
        string json = JsonConvert.SerializeObject(person);
        Console.WriteLine($"基本序列化: {json}");
        
        // 格式化输出
        string formattedJson = JsonConvert.SerializeObject(person, Formatting.Indented);
        Console.WriteLine($"格式化输出:\n{formattedJson}");
        
        Console.WriteLine();
    }
    
    // 2. 基础反序列化
    public static void BasicDeserializationExample()
    {
        Console.WriteLine("2. 基础反序列化示例:");
        
        string json = @"{
            'Name': '李四',
            'Age': 25,
            'Email': 'lisi@example.com',
            'BirthDate': '1998-08-20T00:00:00',
            'Hobbies': ['音乐', '旅行']
        }";
        
        try
        {
            var person = JsonConvert.DeserializeObject<Person>(json);
            Console.WriteLine($"姓名: {person.Name}");
            Console.WriteLine($"年龄: {person.Age}");
            Console.WriteLine($"邮箱: {person.Email}");
            Console.WriteLine($"爱好: {string.Join(", ", person.Hobbies)}");
        }
        catch (JsonException ex)
        {
            Console.WriteLine($"反序列化错误: {ex.Message}");
        }
        
        Console.WriteLine();
    }
    
    // 3. JsonProperty 属性使用
    public static void JsonPropertyAttributeExample()
    {
        Console.WriteLine("3. JsonProperty 属性示例:");
        
        var product = new Product
        {
            Id = 1001,
            Name = "iPhone 15",
            Price = 6999.99m,
            CreatedDate = DateTime.Now,
            IsActive = true,
            Description = "最新款iPhone",
            InternalNotes = "内部备注"
        };
        
        string json = JsonConvert.SerializeObject(product, Formatting.Indented);
        Console.WriteLine($"产品信息:\n{json}");
        
        // 反序列化
        var deserializedProduct = JsonConvert.DeserializeObject<Product>(json);
        Console.WriteLine($"反序列化后: {deserializedProduct.Name} - ¥{deserializedProduct.Price}");
        
        Console.WriteLine();
    }
    
    // 4. JsonIgnore 使用
    public static void JsonIgnoreExample()
    {
        Console.WriteLine("4. JsonIgnore 示例:");
        
        var product = new Product
        {
            Id = 1002,
            Name = "MacBook Pro",
            Price = 12999.99m,
            CreatedDate = DateTime.Now,
            IsActive = true,
            InternalNotes = "这个字段不会被序列化"
        };
        
        string json = JsonConvert.SerializeObject(product, Formatting.Indented);
        Console.WriteLine($"注意 InternalNotes 字段被忽略:\n{json}");
        
        Console.WriteLine();
    }
    
    // 5. 日期时间处理
    public static void DateTimeHandlingExample()
    {
        Console.WriteLine("5. 日期时间处理示例:");
        
        var data = new
        {
            CurrentTime = DateTime.Now,
            UtcTime = DateTime.UtcNow,
            SpecificDate = new DateTime(2024, 1, 1, 12, 0, 0)
        };
        
        // 默认格式
        var settings1 = new JsonSerializerSettings
        {
            DateFormatHandling = DateFormatHandling.IsoDateFormat
        };
        string json1 = JsonConvert.SerializeObject(data, Formatting.Indented, settings1);
        Console.WriteLine($"ISO 格式:\n{json1}");
        
        // 自定义格式
        var settings2 = new JsonSerializerSettings
        {
            DateFormatString = "yyyy-MM-dd HH:mm:ss"
        };
        string json2 = JsonConvert.SerializeObject(data, Formatting.Indented, settings2);
        Console.WriteLine($"自定义格式:\n{json2}");
        
        Console.WriteLine();
    }
    
    // 6. 枚举处理
    public static void EnumHandlingExample()
    {
        Console.WriteLine("6. 枚举处理示例:");
        
        var order = new Order
        {
            OrderId = 12345,
            Status = OrderStatus.Processing,
            TotalAmount = 299.99m
        };
        
        // 默认 - 数字
        string json1 = JsonConvert.SerializeObject(order, Formatting.Indented);
        Console.WriteLine($"默认(数字):\n{json1}");
        
        // 字符串格式
        var settings = new JsonSerializerSettings();
        settings.Converters.Add(new StringEnumConverter());
        string json2 = JsonConvert.SerializeObject(order, Formatting.Indented, settings);
        Console.WriteLine($"字符串格式:\n{json2}");
        
        Console.WriteLine();
    }
    
    // 7. 自定义序列化设置
    public static void CustomSerializationExample()
    {
        Console.WriteLine("7. 自定义序列化设置示例:");
        
        var person = new Person
        {
            Name = "王五",
            Age = 0, // 默认值
            Email = null // null值
        };
        
        var settings = new JsonSerializerSettings
        {
            NullValueHandling = NullValueHandling.Ignore,
            DefaultValueHandling = DefaultValueHandling.Ignore,
            ContractResolver = new CamelCasePropertyNamesContractResolver(),
            Formatting = Formatting.Indented
        };
        
        string json = JsonConvert.SerializeObject(person, settings);
        Console.WriteLine($"自定义设置:\n{json}");
        
        Console.WriteLine();
    }
    
    // 8. JObject 动态操作
    public static void JObjectDynamicExample()
    {
        Console.WriteLine("8. JObject 动态操作示例:");
        
        // 创建 JObject
        var jobject = new JObject
        {
            ["name"] = "赵六",
            ["age"] = 28,
            ["skills"] = new JArray { "C#", "JavaScript", "Python" },
            ["address"] = new JObject
            {
                ["city"] = "北京",
                ["district"] = "朝阳区"
            }
        };
        
        Console.WriteLine($"JObject 创建:\n{jobject.ToString(Formatting.Indented)}");
        
        // 动态修改
        jobject["age"] = 29;
        jobject["skills"].First.AddAfterSelf("Java");
        
        Console.WriteLine($"修改后:\n{jobject.ToString(Formatting.Indented)}");
        
        // 访问属性
        Console.WriteLine($"姓名: {jobject["name"]}");
        Console.WriteLine($"城市: {jobject["address"]["city"]}");
        
        Console.WriteLine();
    }
    
    // 9. LINQ to JSON
    public static void LinqToJsonExample()
    {
        Console.WriteLine("9. LINQ to JSON 示例:");
        
        string json = @"[
            {'name': '张三', 'age': 30, 'department': 'IT'},
            {'name': '李四', 'age': 25, 'department': 'HR'},
            {'name': '王五', 'age': 35, 'department': 'IT'},
            {'name': '赵六', 'age': 28, 'department': 'Finance'}
        ]";
        
        JArray employees = JArray.Parse(json);
        
        // LINQ 查询
        var itEmployees = employees
            .Where(e => e["department"].ToString() == "IT")
            .Select(e => new { 
                Name = e["name"].ToString(), 
                Age = (int)e["age"] 
            });
        
        Console.WriteLine("IT部门员工:");
        foreach (var emp in itEmployees)
        {
            Console.WriteLine($"  {emp.Name}, {emp.Age}岁");
        }
        
        // 统计
        var avgAge = employees.Average(e => (int)e["age"]);
        Console.WriteLine($"平均年龄: {avgAge:F1}");
        
        Console.WriteLine();
    }
    
    // 10. 错误处理
    public static void ErrorHandlingExample()
    {
        Console.WriteLine("10. 错误处理示例:");
        
        string invalidJson = "{ 'name': 'test', 'age': 'invalid_number' }";
        
        var settings = new JsonSerializerSettings
        {
            Error = (sender, args) =>
            {
                Console.WriteLine($"序列化错误: {args.ErrorContext.Error.Message}");
                Console.WriteLine($"路径: {args.ErrorContext.Path}");
                args.ErrorContext.Handled = true;
            }
        };
        
        try
        {
            var person = JsonConvert.DeserializeObject<Person>(invalidJson, settings);
            Console.WriteLine($"处理后: {person?.Name}, Age: {person?.Age}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"未处理的异常: {ex.Message}");
        }
        
        Console.WriteLine();
    }
    
    // 11. 性能优化
    public static void PerformanceOptimizationExample()
    {
        Console.WriteLine("11. 性能优化示例:");
        
        var people = Enumerable.Range(1, 1000)
            .Select(i => new Person 
            { 
                Name = $"Person{i}", 
                Age = 20 + (i % 50),
                Email = $"person{i}@example.com"
            })
            .ToList();
        
        var stopwatch = System.Diagnostics.Stopwatch.StartNew();
        
        // 使用预配置的设置
        var settings = new JsonSerializerSettings
        {
            ContractResolver = new DefaultContractResolver(),
            DateFormatHandling = DateFormatHandling.IsoDateFormat
        };
        
        string json = JsonConvert.SerializeObject(people, settings);
        
        stopwatch.Stop();
        Console.WriteLine($"序列化 {people.Count} 个对象耗时: {stopwatch.ElapsedMilliseconds}ms");
        Console.WriteLine($"JSON 长度: {json.Length} 字符");
        
        Console.WriteLine();
    }
    
    // 12. 自定义 JsonConverter
    public static void JsonConverterExample()
    {
        Console.WriteLine("12. 自定义 JsonConverter 示例:");
        
        var person = new Person
        {
            Name = "自定义转换器测试",
            Age = 30,
            BirthDate = DateTime.Now
        };
        
        var settings = new JsonSerializerSettings();
        settings.Converters.Add(new CustomDateTimeConverter());
        
        string json = JsonConvert.SerializeObject(person, Formatting.Indented, settings);
        Console.WriteLine($"使用自定义转换器:\n{json}");
        
        Console.WriteLine();
    }
    
    // 13. 空值处理
    public static void NullValueHandlingExample()
    {
        Console.WriteLine("13. 空值处理示例:");
        
        var person = new Person
        {
            Name = "测试用户",
            Email = null,
            Hobbies = null
        };
        
        // 包含空值
        var includeNulls = new JsonSerializerSettings
        {
            NullValueHandling = NullValueHandling.Include,
            Formatting = Formatting.Indented
        };
        
        // 忽略空值
        var ignoreNulls = new JsonSerializerSettings
        {
            NullValueHandling = NullValueHandling.Ignore,
            Formatting = Formatting.Indented
        };
        
        Console.WriteLine("包含空值:");
        Console.WriteLine(JsonConvert.SerializeObject(person, includeNulls));
        
        Console.WriteLine("忽略空值:");
        Console.WriteLine(JsonConvert.SerializeObject(person, ignoreNulls));
        
        Console.WriteLine();
    }
    
    // 14. 驼峰命名
    public static void CamelCaseExample()
    {
        Console.WriteLine("14. 驼峰命名示例:");
        
        var product = new Product
        {
            Id = 1,
            Name = "测试产品",
            Price = 99.99m,
            IsActive = true
        };
        
        var camelCaseSettings = new JsonSerializerSettings
        {
            ContractResolver = new CamelCasePropertyNamesContractResolver(),
            Formatting = Formatting.Indented
        };
        
        string json = JsonConvert.SerializeObject(product, camelCaseSettings);
        Console.WriteLine($"驼峰命名:\n{json}");
        
        Console.WriteLine();
    }
}

// 自定义 DateTime 转换器
public class CustomDateTimeConverter : JsonConverter<DateTime>
{
    public override void WriteJson(JsonWriter writer, DateTime value, JsonSerializer serializer)
    {
        writer.WriteValue(value.ToString("yyyy年MM月dd日 HH:mm:ss"));
    }
    
    public override DateTime ReadJson(JsonReader reader, Type objectType, DateTime existingValue, bool hasExistingValue, JsonSerializer serializer)
    {
        string dateString = (string)reader.Value;
        if (DateTime.TryParse(dateString, out DateTime result))
        {
            return result;
        }
        return DateTime.MinValue;
    }
}

// 程序入口点示例
public class Program
{
    public static void Main(string[] args)
    {
        NewtonsoftJsonExamples.RunAllExamples();
        
        Console.WriteLine("按任意键退出...");
        Console.ReadKey();
    }
}