如何用EF快捷查询生成？
如何用EF快捷查询生成？
提问于 2014-04-30 11:17:28
我有保存用户输入的模型，使用EF使用这些数据进行数据库查询构造。所有对角线都是可选的。
我的问题是:查询构建是否可以用更短的方式完成？
具有用户输入的模型：
public class PostFilterModel
{
public PostFilterModel()
{
Currency = Enumerable.Empty<Currency>();
Condition = Enumerable.Empty<Condition>();
Transmission = Enumerable.Empty<Transmission>();
Rudder = Enumerable.Empty<Rudder>();
Body = Enumerable.Empty<Body>();
Engine = Enumerable.Empty<Engine>();
Gear = Enumerable.Empty<Gear>();
}
public int City { get; set; }
public int Region { get; set; }
public int Brand { get; set; }
public int Model { get; set; }
public int MinHorsePower { get; set; }
public int MaxHorsePower { get; set; }
public int MinEngineCapacity { get; set; }
public int MaxEngineCapacity { get; set; }
public int MinMileage { get; set; }
public int MaxMileage { get; set; }
public int MinPrice { get; set; }
public int MaxPrice { get; set; }
public int MinYear { get; set; }
public int MaxYear { get; set; }
public IEnumerable<Currency> Currency { get; set; }
public IEnumerable<Condition> Condition { get; set; }
public IEnumerable<Transmission> Transmission { get; set; }
public IEnumerable<Rudder> Rudder { get; set; }
public IEnumerable<Body> Body { get; set; }
public IEnumerable<Engine> Engine { get; set; }
public IEnumerable<Gear> Gear { get; set; }
}以及基于模型的查询生成器：
public ICollection<Post> GetByFilter(PostFilterModel filter)
{
IQueryable<Post> Posts = uow.PostRepository.GetAll();
if (filter.City > 0)
Posts = Posts.Where(p => p.City.CityId == filter.City);
if (filter.Region > 0)
Posts = Posts.Where(p => p.City.Region.RegionId == filter.Region);
if (filter.Brand > 0)
Posts = Posts.Where(p => p.Car.Brand.BrandId == filter.Brand);
if (filter.Model > 0)
Posts = Posts.Where(p => p.Car.Model.ModelId == filter.Model);
if (filter.MinPrice > 0)
Posts = Posts.Where(p => p.Price >= filter.MinPrice);
if (filter.MaxPrice > 0)
Posts = Posts.Where(p => p.Price <= filter.MaxPrice);
if (filter.MinYear > 0)
Posts = Posts.Where(p => p.Car.Year >= filter.MinYear);
if (filter.MaxYear > 0)
Posts = Posts.Where(p => p.Car.Year <= filter.MaxYear);
if (filter.Condition.Count() > 0)
Posts = Posts.Where(p => filter.Condition.Contains(p.Car.Condition));
if (filter.Transmission.Count() > 0)
Posts = Posts.Where(p => filter.Transmission.Contains(p.Car.Transmission));
if (filter.Rudder.Count() > 0)
Posts = Posts.Where(p => filter.Rudder.Contains(p.Car.Rudder));
if (filter.Body.Count() > 0)
Posts = Posts.Where(p => filter.Body.Contains(p.Car.Body));
if (filter.Engine.Count() > 0)
Posts = Posts.Where(p => filter.Engine.Contains(p.Car.Engine));
if (filter.Gear.Count() > 0)
Posts = Posts.Where(p => filter.Gear.Contains(p.Car.Gear));
return Posts.ToList();
}回答 1
Stack Overflow用户
回答已采纳
发布于 2014-05-01 05:49:49
我不知道您为什么要使用更少的代码，我更喜欢可读性而不是更少的代码。我唯一想做的事情是，在不破坏可读性的情况下，将所有逻辑合并到一个Where子句中，类似于：
public ICollection<Post> GetByFilter(PostFilterModel filter)
{
return uow.PostRepository.GetAll().Where(p =>
(filter.City <= 0 || p.City.CityId == filter.City) &&
(filter.Region <= 0 || p.Region.RegionId == filter.Region) &&
(filter.Brand <= 0 || p.Car.Brand.BrandId == filter.Brand) &&
(filter.Model <= 0 || p.Car.Model.ModelId == filter.Model) &&
(filter.MinPrice <= 0 || p.Price >= filter.MinPrice) &&
(filter.MaxPrice <= 0 || p.Price <= filter.MaxPrice) &&
(filter.MinYear <= 0 || p.Car.Year >= filter.MinYear) &&
(filter.MaxYear <= 0 || p.Car.Year <= filter.MaxYear) &&
(filter.Condition.Count() <= 0 || filter.Condition.Contains(p.Car.Condition)) &&
(filter.Transmission.Count() <= 0 || filter.Transmission.Contains(p.Car.Transmission)) &&
(filter.Rudder.Count() <= 0 || filter.Rudder.Contains(p.Car.Rudder)) &&
(filter.Body.Count() <= 0 || filter.Body.Contains(p.Car.Body)) &&
(filter.Engine.Count() <= 0 || filter.Engine.Contains(p.Car.Engine)) &&
(filter.Gear.Count() <= 0 || filter.Gear.Contains(p.Car.Gear)) &&
);
}但你并不是真的存钱。
您可以通过在筛选器上存储子句来使用查询的动态生成，但这只是将代码移到其他地方，并将依赖关系构建到代码中。
我恳请您不要使用单行if语句(即没有大括号)，因为这是一个等待发生的错误。
我的观点是，保持代码的可读性，而不是简短。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/23386686
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