如何优化 linq 查询 c# 复杂 object？

Question

我正在制作一个返回访问者数据的方法，使用 linq c # 进行此查询，如下所示，

public async Task<Models.Visitor> GetVisitorByEmail(string email)
{
    return (from v in _unitOfWorkModel.Repository<Visitor>().GetList()
            where v.Email.ToLower() == email.ToLower()
            select new Models.Visitor
            {
                VisitorId = v.VisitorId,
                FirstName = v.FirstName,
                SecondName = v.SecondName,
                FirstLastName = v.FirstLastName,
                SecondLastName = v.SecondLastName,
                Gender = (from g in _unitOfWorkModel.Repository<Gender>().GetList()
                          where g.GenderId == v.GenderId
                          select new Models.Gender
                          {
                              GenderId = g.GenderId,
                              GenderName = g.GenderName,
                          }).FirstOrDefault(),
                Email = v.Email,
                Telephone = v.Telephone,
                Family = (from vf in _unitOfWorkModel.Repository<VisitorFamily>().GetList()
                          join f in _unitOfWorkModel.Repository<Family>().GetList()
                          on vf.FamilyId equals f.FamilyId
                          where vf.VisitorId == v.VisitorId
                          select new Models.Family
                          {
                              FamilyId = f.FamilyId,
                              FamilyName = f.FamilyName,
                              PhotoPath = f.PhotoPath
                          }).ToList(),
                Territory = (from vt in _unitOfWorkModel.Repository<VisitorTerritory>().GetList()
                             join t in _unitOfWorkModel.Repository<Territory>().GetList()
                             on vt.TerritoryId equals t.TerritoryId
                             where vt.VisitorId == v.VisitorId
                             select new Models.Territory
                             {
                                 TerritoryId = t.TerritoryId,
                                 TerritoryName = t.TerritoryName,
                                 Axis = (from a in _unitOfWorkModel.Repository<Axis>().GetList()
                                         where a.AxisId == t.AxisId
                                         select new Models.Axis
                                         {
                                             AxisId = a.AxisId,
                                             AxisName = a.AxisName,
                                         }).FirstOrDefault(),
                             }).ToList(),
                IsActive = v.IsActive,
                PhotoPath = v.PhotoPath,
                UserTypeId = v.UserTypeId,
                UserId = v.UserId,
                CreateBy = v.CreateBy,
                CreationDate = v.CreationDate,
                ModifiedBy = v.ModifiedBy,
                ModifiedDate = v.ModifiedDate,
            }).FirstOrDefault();
}

例如，我想知道我是否有 20 个访问者，如果我正在开发的 api 会给我良好的响应时间，或者是否有另一种更优化的方法来做到这一点，因为我不熟悉使用 linq Z4A8A036F09D347B737 创建复杂对象我正在使用 ASP.NET CORE 3.1 和核心实体框架，

我将不胜感激帮助您优化此查询。

我很注意你的建议

Answer 1

这是您必须附加所有嵌套实体的样式示例：

public Task<IQueryable<Models.Gender>> GetGenderById(int id)
{
    return _unitOfWorkModel.Repository.Get<Gender>(x => x.GenderId = id).
}

在此示例中，您将在 SQL 服务器上传递查询，并通过ToList() （在GetVisitorByEmail()方法中）在一条记录中返回结果。

默认情况下， Get()方法必须在您的基础存储库中，并且您的所有存储库都必须继承它，并将其实体类型传递给：

public abstract class BaseRepository<T> : IBaseRepository<T> where T : class
    {
        protected readonly ApplicationDbContext DbContext;
        protected readonly DbSet<T> DbSetEntity;
        private readonly ILogger<BaseRepository<T>> _logger;

        protected BaseRepository(ApplicationDbContext dbContext,ILoggerFactory loggerFactory)
        {
            DbContext = dbContext;
            DbSetEntity = DbContext.Set<T>();

            _logger = loggerFactory.CreateLogger<BaseRepository<T>>();
        }

        ...

        public virtual T Get(Expression<Func<T, bool>> predicate)
        {
            return DbContext.Set<T>().FirstOrDefault(predicate);
        }

并使用此方法：

return (from v in _unitOfWorkModel.Repository<Visitor>
            where v.Email.ToLower() == email.ToLower()
            select new Models.Visitor
            {
                VisitorId = v.VisitorId,
                FirstName = v.FirstName,
                SecondName = v.SecondName,
                FirstLastName = v.FirstLastName,
                SecondLastName = v.SecondLastName,
                Gender = GetGenderById(v.GenderId).ToList(),
                Email = v.Email
...