如何在 class 中从 appsettings.json 获取 ConnectionString？

Question

我正在尝试连接到我的数据库而不对连接字符串进行硬编码。 这就是我想出的，有什么聪明的方法来获取 ConnectionString 吗？

安全道 class：

public class SecurityDAO
    {
        internal bool FindByUser(UserModel user)
        {
            string connectionString = "";
            bool success = false;

            string queryString = "SELECT * FROM users WHERE username = @username AND password = @password";

            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand command = new MySqlCommand(queryString, connection);

                command.Parameters.Add("@username", MySqlDbType.VarChar, 50).Value = user.Username;
                command.Parameters.Add("@password", MySqlDbType.VarChar, 50).Value = user.Password;

                try
                {
                    connection.Open();
                    MySqlDataReader reader = command.ExecuteReader();

                    if (reader.HasRows)
                    {
                        success = true;
                    }
                    else
                    {
                        success = false;
                    }
                }
                catch (Exception ex)
                {
                    throw ex;
                }
            }
            return success;
        }
    }

安全服务 class：

public class SecurityService
    {
        SecurityDAO daoService = new SecurityDAO();

        public bool Authenticate(UserModel user)
        {
            return daoService.FindByUser(user);
        }
    }

Answer 1

您需要使用构造函数注入它

public SecurityDAO(IConfiguration configuration)
{
    this.configuration = configuration;
}

Answer 2

您可以使用 DI 在您使用 SecurityService 的地方获取 IConfiguration 并将 IConfiguration 传递给 SecurityService.Authenticate。这是一个演示：

启动.cs：

public void ConfigureServices(IServiceCollection services)
        {
            ...

            services.AddSingleton<IConfiguration>(Configuration);
           
            services.AddScoped<SecurityService, SecurityService>();

        }

Controller：

public class Test2Controller : Controller
    {
        IConfiguration _Configuration;
        SecurityService _securityService;
        public Test2Controller(IConfiguration Configuration, SecurityService securityService) {
            _Configuration = Configuration;
            _securityService = securityService;
        }
        public IActionResult Index()
        {
            var s=_securityService.Authenticate(new UserModel(), _Configuration);
            return Ok();
        }
    }

安保服务：

SecurityDAO daoService = new SecurityDAO();

        public bool Authenticate(UserModel user,IConfiguration Configuration)
        {
            return daoService.FindByUser(user, Configuration);
        }

安全道：

public class SecurityDAO
    {
        internal bool FindByUser(UserModel user, IConfiguration Configuration)
        {
            string connectionString = Configuration["ConnectionStrings:DefaultConnection"];
            return true;
        }
    }

结果：

Answer 3

如果不想使用DI，可以这样获取appsettings.json中的数据：

var configuration = new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory()).AddJsonFile("appsettings.json").Build();
var connectionString = configuration.GetConnectionString("XXXX");