c# 做个1分钟定时执行将sql语句查询type=2 的值循环插入json{"a":"a","b":[{"c":"c","d":"d"},{"c":"c","d":"d"}] }发送post请求，得到返回值json{"aa":"aa"}，根据返回修改type=3

您可以按照以下步骤来实现您的需求：
1. 使用C#中的定时器Timer，设置定时器的时间间隔为1分钟，然后在定时器的Elapsed事件中编写查询type=2的SQL语句并将结果循环插入到一个List中。
2. 使用Newtonsoft.Json库将List转换为JSON字符串，然后发送POST请求并获取返回值。
3. 使用Newtonsoft.Json库将返回值JSON字符串转换为对象，然后修改其中type=3的值。
4. 将修改后的对象转换为JSON字符串，然后发送POST请求并获取返回值。

下面是示例代码：

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Net.Http;
using Newtonsoft.Json;

public class Program
{
    private static Timer _timer;

    public static void Main()
    {
        _timer = new Timer(60000); // 1分钟
        _timer.Elapsed += OnTimerElapsed;
        _timer.Start();

        Console.ReadLine();
    }

    private static void OnTimerElapsed(object sender, ElapsedEventArgs e)
    {
        var list = new List<object>();

        using (var connection = new SqlConnection("your_connection_string"))
        {
            connection.Open();

            using (var command = new SqlCommand("SELECT * FROM your_table WHERE type = 2", connection))
            {
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        var obj = new
                        {
                            c = reader.GetString(reader.GetOrdinal("c")),
                            d = reader.GetString(reader.GetOrdinal("d"))
                        };

                        list.Add(obj);
                    }
                }
            }
        }

        var json = JsonConvert.SerializeObject(new { a = "a", b = list });

        using (var client = new HttpClient())
        {
            var content = new StringContent(json, Encoding.UTF8, "application/json");
            var response = client.PostAsync("your_url", content).Result;
            var responseJson = response.Content.ReadAsStringAsync().Result;
            var responseObj = JsonConvert.DeserializeObject<Dictionary<string, string>>(responseJson);

            if (responseObj.ContainsKey("aa"))
            {
                var aa = responseObj["aa"];

                var obj = JsonConvert.DeserializeObject<dynamic>(json);

                foreach (var item in obj.b)
                {
                    if (item.c == "c" && item.d == "d")
                    {
                        item.type = 3;
                    }
                }

                var modifiedJson = JsonConvert.SerializeObject(obj);

                var modifiedContent = new StringContent(modifiedJson, Encoding.UTF8, "application/json");
                var modifiedResponse = client.PostAsync("your_url", modifiedContent).Result;
                var modifiedResponseJson = modifiedResponse.Content.ReadAsStringAsync().Result;
            }
        }
    }
}