加入内部列表

Question

我有这个linq查询：

var investorData = from investor in db.Investors
                        join investorLine in db.InvestorStatementLines
                            on investor.InvestorID equals investorLine.InvestorID
                        where investor.UserId == userId
                        select new InvestorViewModel()
                        {
                            InvestorId = investor.InvestorID,
                            InvestorName = investor.Name,
                            FundingDate = investor.FundingDate,
                            DueDate = investor.DueDate,
                            FundsCommitted = investor.FundsCommitted,
                            FundsInvested = investor.FundsInvested,
                            StatementLines =
                                db.InvestorStatementLines.Where(s => s.InvestorID == investor.InvestorID)
                                    .Select(t => new InvestorStatementLineVM
                                    {
                                        Balance = t.Balance,
                                        Credit = t.Credit,
                                        Debit = t.Debit,
                                        InvestorStatementLineDetails = t.Details,
                                        Date = t.Date
                                    }).ToList()
                        };

视图模型：

public class InvestorViewModel
{
    public int InvestorId { get; set; }
    public string InvestorName { get; set; }
    public DateTime FundingDate { get; set; }
    public DateTime? DueDate { get; set; }
    public Decimal? FundsCommitted { get; set; }
    public Decimal? FundsInvested { get; set; }
    public List<InvestorStatementLineVM>  StatementLines { get; set; }
}

发生的事情是，一旦我执行查询，我就会获得125条记录，这就是该投资者的StatementLines数量。所以我得到了125条相同的记录，但我期待一个结果，它将在内部列表中包含125条语句行。

这个查询是否正确？

Answer 1

1. 使用GroupJoin而不是Join：（

   _join x in y on x.a equals y.a
   into z_

   ）

   var investorData = from investor in db.Investors
                           join investorLine in db.InvestorStatementLines
                           on investor.InvestorID equals investorLine.InvestorID
                           into investorLine
                           where investor.UserId == userId
   
                           select new InvestorViewModel()
                           {
                               InvestorId = investor.InvestorID,
                               InvestorName = investor.Name,
                               FundingDate = investor.FundingDate,
                               DueDate = investor.DueDate,
                               FundsCommitted = investor.FundsCommitted,
                               FundsInvested = investor.FundsInvested,
                               StatementLines = investorLine
                                   .Select(t => new InvestorStatementLineVM
                                   {
                                       Balance = t.Balance,
                                       Credit = t.Credit,
                                       Debit = t.Debit,
                                       InvestorStatementLineDetails = t.Details,
                                       Date = t.Date
                                   }).ToList()
                           };

   而不是执行子查询只是使用您刚刚执行的联接中的数据。
2. 一个更好的选择，使用实体框架，使用navigation properties然后你不需要执行连接，但你只需要InvestorStatementLines作为你的investor的属性。 要设置导航属性：

   public class InvestorViewModel
   {
       public int InvestorId { get; set; }
       public string InvestorName { get; set; }
       public DateTime FundingDate { get; set; }
       public DateTime? DueDate { get; set; }
       public Decimal? FundsCommitted { get; set; }
       public Decimal? FundsInvested { get; set; }
       public virtual ICollection<InvestorStatementLineVM>  StatementLines { get; set; }
   }

   查询将如下所示：

   var investorData = from investor in db.Investors
                      where investor.UserId == userId
                      select new InvestorViewModel()
                      {
                          InvestorId = investor.InvestorID,
                          ....
                          StatementLines = investor.InvestorStatementLines.Select(....)
                      };

Answer 2

这是您使用导航属性执行此操作的方法

var investorData = from investor in db.Investors
                   where investor.UserId == userId
                   select new InvestorViewModel()
                   {
                       InvestorId = investor.InvestorID,
                       InvestorName = investor.Name,
                       FundingDate = investor.FundingDate,
                       DueDate = investor.DueDate,
                       FundsCommitted = investor.FundsCommitted,
                       FundsInvested = investor.FundsInvested,
                       StatementLines = investor.InvestorStatementLines
                           .Select(t => new InvestorStatementLineVM
                           {
                               Balance = t.Balance,
                               Credit = t.Credit,
                               Debit = t.Debit,
                               InvestorStatementLineDetails = t.Details,
                               Date = t.Date
                           }).ToList()
                   };