Question

所以我得到了地址表和合同表。我想遍历所有合同并从中生成一些Dto，但要使用地址名称和编号而不是id（guid）。我的问题是合同表中的地址表上有4个外键。我仍然可以通过某种方式甚至是多个联接来做到这一点吗？

这是我目前正在尝试的方法：

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我的另一种方法可能会生成太多查询：

  var contracts = context.Contracts
    .Join(context.Addresses, 
       (con => con.AddressId), 
       (adr => adr.AddressId), 
       (con,adr) 
       => new { contractInfo = con, addressInfo = adr });

      foreach(var a in contracts) {
          new MyDto() {
            AddressId = a.addressInfo.AddressNumber,
            AddressName = a.addressInfo.FullName,
            Date= a.contractInfo.Date,
            AnotherDate = a.contractInfo.AnotherDate,
            Text = a.contractInfo.Text,
            VerweisAdrId = a.addressInfo. // ???
            VerweisAdrName = a.addressInfo. // 2 more cases like this would follow
          }
        }

Answer 1

var contracts = context.Contracts
    .Join(context.Addresses, 
       (con => con.AddressId), 
       (adr => adr.AddressId), 
       (con,adr) 
       => new { contractInfo = con, addressInfo = adr })
    .Join(context.Addresses,
        ca => ca.contractInfo.VerweisAdrId,
        adr => adr.AddressId,
        (ca, adr) => new { ca.contractInfo, ca.addressInfo, verweisAdr = adr })
    // ... and so on
    .Select(cavwx => new MyDto() {
        AddressId = cavwx.addressInfo.AddressNumber,
        AddressName = cavwx.addressInfo.FullName,
        VerweisAdrId = cavwx.verweisAdr.AddressNumber,
        VerweisAdrName = cavwx.verweisAdr.FullName,
        // ... and so on
     });

Linq使用4个不同的外键连接同一张表

1 个答案: