如何改进此 Entity Framework 查询

Question

我有以下实体：

申请人：人
电话号码
电话类型

申请人来自Person。 Applicant 有很多 PhoneNumber（最多三个）。每个PhoneNumber只有1个PhoneType.

public class Applicant : Person
{    
    public virtual ICollection<PhoneNumber> PhoneNumbers { get; set; }
}

public class PhoneNumber 
{                        
    public int PersonId { get; set; }

    [Required]
    [MaxLength(17)]
    public string Number { get; set; }    

    public int PhoneTypeId { get; set; }            

    public virtual PhoneType PhoneType { get; set; }

}

public class PhoneType 
{     
    [Required]
    [MaxLength(24)]
    public string Name { get; set; }

    public virtual ICollection<PhoneNumber> PhoneNumbers { get; set; }
}

在我看来，我正在使用的两个查询可以合并，并且可以消除 foreach 循环，但我在第一个查询中已经有大量连接，我不确定如何合并它们。这个问题是一个两部分的问题：

如何合并这两个查询和
如果我不合并查询，我如何改进 PhoneNumber / PhoneType 查询。

目标是 return 一个 Applicant 和一个 PhoneNumber 列表，每个 PhoneNumber 一个 PhoneType。为清楚起见，类型为：家庭、办公室和移动。

/*------------------------------------------*/
/* Obtain the Applicant                     */
/*------------------------------------------*/
IQueryable<Applicant> applicantQuery = 
      DbContext.Applicants.Where(a => a.CreatedBy == userId)
               .Include(applicant => applicant.Address)
               .Include(applicant => applicant.Address.StateProvince)
               .Include(applicant => applicant.PhoneNumbers)                                                
               .Include(applicant => applicant.HomeChurch)
               .Include(applicant => applicant.HomeChurch.Address)
               .Include(applicant => applicant.HomeChurch.Address.StateProvince)
               .Include(applicant => applicant.TripApplication);

Applicant applicant = applicantQuery.FirstOrDefault<Applicant>();

if (applicant != null && applicant.PhoneNumbers != null)
{
    IQueryable<PhoneType> phoneTypeQuery = DbContext.Set<PhoneType>();
    List<PhoneType> phoneTypes = phoneTypeQuery.ToList<PhoneType>();

    foreach (PhoneNumber ph in applicant.PhoneNumbers)
    {
        ph.PhoneType = (phoneTypes.Where(pt => pt.Id == ph.PhoneTypeId)).First();
    }
}

提前感谢您提供的任何帮助。

Answer 1

EF Core 通过组合 Include() 和 ThenInclude() 支持加载多个级别，更多信息 here

要加载 Phone 以及 Phone 类型，您的查询应如下所示（为清楚起见，我删除了其余关系）：

var applicant = DbContext.Applicants.Where(a => a.CreatedBy == userId)
        .Include(applicant => applicant.PhoneNumbers)                                                
        .ThenInclude(phone => phone.PhoneType)
        .FirstOrDefault();

如何改进此 Entity Framework 查询

How to Improve on this Entity Framework Query

sql-server

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linq-to-sql

entity-framework-core