DbContextOptions參數ASP.net核心

Question

我收到ArgumentNullException：值不能為null。 參數名稱：options我認為這是因為我的默認構造函數使我為null，但是如果我注釋掉該構造函數，則該類的新實例需要的參數我不知道要提供什么。

 public class OvertimeRequestBusiness
    {
        public static OvertimeRequestBusiness Instance { get; } = new OvertimeRequestBusiness();
        private readonly DbContextOptions<DatabaseContext> _contextOptions;
     //default ctor
   public OvertimeRequestBusiness() : base() { }


        public OvertimeRequestBusiness(DbContextOptions<DatabaseContext> contextOptions)
        {
            _contextOptions = contextOptions;
        }
        public async Task<List<User>> GetAllUsersAsync()
        {
            using (var ctx = new DatabaseContext(_contextOptions))
            {
                var query = ctx.Users;
                var res = await query.ToListAsync();
                return res;
            }
        }
    }

在我的控制器中

  [Route("users")]
        [HttpGet]
        public async Task<List<User>> GetAllUsers()
        {
          return await OvertimeRequestBusiness.Instance.GetAllUsersAsync();
        }

Answer 1

這是創建DbContextOptions ：

var optionsBuilder = new DbContextOptionsBuilder<DatabaseContext>();
optionsBuilder.UseSqlServer("connection_string_here");

然后DbContextOptions<DatabaseContext>將作為optionsBuilder.Options可用。 您可以將其傳遞給OvertimeRequestBusiness.ctor ：

new OvertimeRequestBusiness(optionsBuilder.Options);