将 SQL 转换为 C# 实体框架 Linq

Question

我基本上想要做的是获取所有尚未为特定位置分配包裹位置价格的包裹...

我有以下 SQL：

  SELECT *  FROM Package
  LEFT JOIN PackageLocationPrices ON Package.Id = PackageLocationPrices.PackageId
  Where PackageLocationPrices.LocationId IS NULL

如何将其转换为 Linq 到实体？

我试过这样的事情：

this.db.Packages.Include(p => p.PackageLocationPrices).Where(p => p.Id == p.PackageLocationPrices.????).ToList();

我可以加入包裹位置价格，但我无法获得包裹位置价格的属性来执行上面的 SQL？ 下面是我的架构...... PackageLocationPrices.PackageId 是 Package.Id 的外键

包裹实体：

    public partial class Package
{
    public Package()
    {
        this.DiscountCodes = new HashSet<DiscountCode>();
        this.PackageLocationPrices = new HashSet<PackageLocationPrice>();
        this.Memberships = new HashSet<Membership>();
    }

    public int Id { get; set; }
    public string Name { get; set; }
    public int PackageOrder { get; set; }
    public int PackageTypeId { get; set; }
    public int PackagePeriodDays { get; set; }
    public int PackagePeriodMonths { get; set; }
    public int PackageSuspensionLimit { get; set; }
    public int PackageSuspensionLimitIfAdminOverride { get; set; }
    public int PackageSuspensionMinLength { get; set; }
    public int PackageSuspensionMaxLength { get; set; }
    public int PackageSuspensionsMaxLengthCombined { get; set; }
    public int PackagePaymentHolidayLimit { get; set; }
    public int PackagePaymentHolidayMinLength { get; set; }
    public int PackagePaymentHolidayMaxLength { get; set; }
    public int PackageVisitLimit { get; set; }
    public bool PackageIsActive { get; set; }
    public bool PackageIsReoccuring { get; set; }
    public bool PackagePayInFull { get; set; }
    public bool PackageIsSession { get; set; }
    public System.DateTime CreatedDate { get; set; }
    public System.DateTime ModifiedDate { get; set; }
    public string CreatedBy { get; set; }
    public string ModifiedBy { get; set; }

    public virtual AspNetUser AspNetUserCreatedBy { get; set; }
    public virtual AspNetUser AspNetUserModifiedBy { get; set; }
    public virtual ICollection<DiscountCode> DiscountCodes { get; set; }
    public virtual PackageType PackageType { get; set; }
    public virtual ICollection<PackageLocationPrice> PackageLocationPrices { get; set; }
    public virtual ICollection<Membership> Memberships { get; set; }
}

包裹位置价格实体：

    public partial class PackageLocationPrice
{
    public int Id { get; set; }
    public int LocationId { get; set; }
    public int PackageId { get; set; }
    public decimal MonthlyPrice { get; set; }
    public decimal TotalPrice { get; set; }
    public System.DateTime CreatedDate { get; set; }
    public System.DateTime ModifiedDate { get; set; }
    public string CreatedBy { get; set; }
    public string ModifiedBy { get; set; }

    public virtual AspNetUser AspNetUserCreatedBy { get; set; }
    public virtual AspNetUser AspNetUserModifiedBy { get; set; }
    public virtual Location Location { get; set; }
    public virtual Package Package { get; set; }
}

Answer 1

var result = (from p in Package
            join q in PackageLocationPrices on p.Id equals q.PackageId into pq
            from r in pq.DefaultIfEmpty()
            select new {p, r}).ToList();

这应该返回与您的 SQL 查询完全相同的内容。

Answer 2

我认为您可以从另一个角度创建查询：

var query=(from pl in db.PackageLocationPrices
           where pl.LocationId == null
           select pl.Package).ToList();

如果您禁用了延迟加载，则还需要使用Include扩展方法：

var query=(from pl in db.PackageLocationPrices.Include(p=>p.Package)
           where pl.LocationId == null
           select pl.Package).ToList();

使用方法语法是这样的：

var query=db.PackageLocationPrices.Include(p=>p.Package)
                                  .Where(pl=>pl.LocationId == null)
                                  .Select(pl=>pl.Package)
                                  .ToList();

如果您想要同时使用Package和PackageLocationPrice ，请执行以下操作：

 var query=db.PackageLocationPrices.Include(p=>p.Package)
                                   .Where(pl=>pl.LocationId == null)
                                   .ToList();

通过最后一个查询，您将获得PackageLocationPrice的列表，如果您想查看给定PackageLocationPrice的相关Package ，您可以使用Package导航属性。