为什么响应体是空的？

如果正确输入了登录名和密码，我编写了一个返回所有用户数据的身份验证。这里一切都很好。数据库管理器文件代码：

public static User AuthUser(User user)
    {
        if (sqlConnection.State == System.Data.ConnectionState.Closed)
            sqlConnection.Open();
        try
        {
            SqlCommand command = new SqlCommand(
                $"SELECT * FROM [Users] WHERE login = @login AND password = @password",
                sqlConnection);
            command.Parameters.AddWithValue("login", user.login);
            command.Parameters.AddWithValue("password", user.password);

            SqlDataReader reader = command.ExecuteReader();
            if (reader.Read())
            {
                user.id = Convert.ToInt32(reader.GetValue(0));
                user.lastName = Convert.ToString(reader.GetValue(1));
                user.firstName = Convert.ToString(reader.GetValue(2));
                user.patronymic = Convert.ToString(reader.GetValue(3));
                user.phoneNumber = Convert.ToString(reader.GetValue(4));
                user.address = Convert.ToString(reader.GetValue(5));
                user.role = (Role)Convert.ToInt16(reader.GetValue(8));
            }
                sqlConnection.Close();
                return user;
        }
        catch
        {
            sqlConnection.Close();
            return user;
        }
    }

用户控制器文件代码：

[HttpPost("~/Authentication")]
    public User Authentication(string login, string password)
    {
        return DataBaseManager.AuthUser(
            new User(login, password));
    }

它返回：

接下来，我想接收运输公司的所有信息，但实际上，将参数传递给我没有任何意义。数据库管理器文件代码：

public static SDEK GetInfoSDEK(SDEK sdek)
    {
        if (sqlConnection.State == System.Data.ConnectionState.Closed)
            sqlConnection.Open();
        try
        {
            SqlCommand command = new SqlCommand(
                $"SELECT * FROM [TransportCompanies] WHERE name = @name",
                sqlConnection);
            command.Parameters.AddWithValue("name", sdek.name);

            SqlDataReader reader = command.ExecuteReader();
            if (reader.Read())
            {
                sdek.id = Convert.ToInt32(reader.GetValue(0));
                sdek.price_km = Convert.ToDecimal(reader.GetValue(2));
                sdek.price_kg = Convert.ToDecimal(reader.GetValue(3));
                sdek.price_insurance = Convert.ToDecimal(reader.GetValue(4));
            }
            sqlConnection.Close();
            return sdek;
        }
        catch
        {
            sqlConnection.Close();
            return sdek;
        }
    }

TransportCompanyController 文件代码：

[HttpGet("~/GetInfoSDEK")]
    public SDEK GetInfoSDEK()
    {
        return DataBaseManager.GetInfoSDEK(new SDEK());
    }

回报：

我要求它返回一个 SDEK 类的实例，但它没有。我通过调试检查了它 - 它写入并查看所有数据。SDEK 类作为库包含（通过分配）。

问题：我做错了什么？

更新：“显示用户和 SDEK 数据模型”

用户型号：

    namespace DeliveryApp
{
    public enum Role
    {
        User,
        Admin
    }
    public class User
    {
        public int id { get; set; }
        public string lastName { get; set; }
        public string firstName { get; set; }
        public string patronymic { get; set; }
        public string phoneNumber { get; set; }
        public string address { get; set; }
        public string login { get; set; }
        public string password { get; set; }
        public Role role { get; set; }


        public User(string lastName, string firstName, string patronymic, string phoneNumber, string address, string login, string password, Role role = Role.User)
        {
            this.lastName = lastName;
            this.firstName = firstName;
            this.patronymic = patronymic;
            this.phoneNumber = phoneNumber;
            this.address = address;
            this.login = login;
            this.password = password;
            this.role = role;
        }
        public User(string login, string password)
        {
            this.login = login;
            this.password = password;
        }
    }
}

SDEK 型号：

namespace TransportCompany1
{
    public class SDEK
    {
        public int id = -1;
        public string name = "SDEK";
        public decimal price_km = 0;
        public decimal price_kg = 0;
        public decimal price_insurance = 0;

        public SDEK(int id, string name, decimal price_km, decimal price_kg, decimal price_insurance) // СЕРВЕР: Отвечает клиенту, если такая транспортная компания существует.
        {
            this.id = id;
            this.name = name;
            this.price_km = price_km;
            this.price_kg = price_kg;
            this.price_insurance = price_insurance;
        }
        public SDEK() { }
    }
}