前言

技术群里面一个哥们在群里提了一个问题，怎么把Json的树形结构展平成一层
在线Json格式化工具

将这个JSON

展平成这样

代码

使用方法

static void Main(string[] args)
{
    //将测试对象转换成测试Json
    var json = JsonConvert.SerializeObject(new
    {
        Id = 1,
        Name = "张三",
        Childs = new[]
        {
            new
            {
                Id = 2,
                Name = "李四"
            },
            new
            {
                Id = 3,
                Name = "王五"
            }
        },
        Dogs = new []
        {
            new
            {
                Id = 10,
                DogName = "来福"
            }
        }
    });
    //使用Newtonsoft.Json解析Json字符串获取Json结构对象
    var jObject = (JToken)JsonConvert.DeserializeObject(json);
    //调用展平Json函数得到展平后的对象列表
    var result = FlattenJsonUtil.Flatten(jObject, null);
    //将展平后的对象列表转换成Json字符串
    var rJson = FlattenJsonUtil.ToJson(result);
    //将展平后的Json字符串输出到控制台上
    Console.WriteLine(rJson);
}

展平Json帮助类

public class FlattenJsonUtil
{
    public class JsonKey
    {
        /// <summary>
        /// 键名称
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 父亲节点
        /// </summary>
        public JsonKey Parent { get; set; }

        /// <summary>
        /// 创建新Key
        /// </summary>
        public static JsonKey CreateKey(JsonKey parentKey, string name)
        {
            return new JsonKey
            {
                Parent = parentKey,
                Name = name
            };
        }

        public override string ToString()
        {
            var names = new List<string>();
            for (var i = this; i != null; i = i.Parent)
            {
                names.Add(i.Name);
            }

            names.Reverse();
            return string.Join("_", names);
        }
    }

    public class JsonNode
    {
        /// <summary>
        /// 键值
        /// </summary>
        public JsonKey Key { get; set; }

        /// <summary>
        /// 字符串、数字、null、日期
        /// </summary>
        public string Value { get; set; }

        /// <summary>
        /// 前面的节点
        /// </summary>
        public JsonNode Previous { get; set; }

        /// <summary>
        /// 复制并设置前面对象
        /// </summary>
        public JsonNode CopyAndSetPrevious(JsonNode jsonNode)
        {
            List<JsonNode> nodes = new List<JsonNode>()
            {
                this
            };
            var top = this;
            while (top.Previous != null)
            {
                top = top.Previous;
                nodes.Add(top);
            }

            var last = jsonNode;
            //循环克隆一遍
            for (var i = nodes.Count - 1; i >= 0; i--)
            {
                var node = nodes[i];
                last = new JsonNode
                {
                    Key = node.Key,
                    Previous = last,
                    Value = node.Value
                };
            }

            return last;
        }

        public override string ToString()
        {
            var items = new List<string>();
            for (var i = this; i != null; i = i.Previous)
            {
                items.Add($"\"{i.Key}\":{i.Value}");
            }

            items.Reverse();
            return $"{{{string.Join(",", items)}}}";
        }
    }

    public static string ToJson(List<JsonNode> nodes)
    {
        return $"[{string.Join(",", nodes)}]";
    }

    /// <summary>
    /// 展平Json
    /// </summary>
    public static List<JsonNode> Flatten(JToken json, JsonKey parentKey)
    {
        //对象
        if (json.Type == JTokenType.Object)
        {
            List<JsonNode> result = new List<JsonNode>();
            foreach (var property in ((JObject)json).Properties())
            {
                var key = JsonKey.CreateKey(parentKey, property.Name);
                var value = Flatten(property.Value, key);
                result = MergeJsonNodes(result, value);
            }

            return result;
        }

        if (json.Type == JTokenType.Array)
        {
            List<JsonNode> result = new List<JsonNode>();
            foreach (var jToken in (JArray)json)
            {
                var value = Flatten(jToken, parentKey);
                result.AddRange(value);
            }

            return result;
        }

        return new List<JsonNode>
        {
            new JsonNode
            {
                Key = parentKey,
                Value = JsonValueToString(json)
            }
        };
    }

    private static string JsonValueToString(JToken json)
    {
        if (json.Type == JTokenType.String || json.Type == JTokenType.Date)
        {
            return $"\"{json}\"";
        }

        return json.ToString();
    }

    /// <summary>
    /// 合并结果集
    /// </summary>
    private static List<JsonNode> MergeJsonNodes(List<JsonNode> result, List<JsonNode> value)
    {
        if (result.Count == 0)
        {
            return value;
        }

        if (value.Count == 1)
        {
            var first = value.First();
            return result.Select(x => first.CopyAndSetPrevious(x)).ToList();
        }

        return result.SelectMany(r => value.Select(v => v.CopyAndSetPrevious(r))).ToList();
    }
}