Question

我有一个类结构如下（每个子类可以有任意数量，也可以有多个Masters）。我想使用linq查询来获取Subfolios的扁平列表，并按Subfolio的“Index”属性进行过滤。

我想我可以使用以下方法获取Master的子文件夹：

IEnumerable< Subfolio> result = from dd in devices.Master
                     where dd.ID == 14
                     from pfo in dd. Portfolio
                     from folio in pfo.Folio
                     from subfolio in folio.Subfolio
                     where subfolio.Ind == 32
                     select subfolio;

或者

IEnumerable<Subfolio> result =
            devices.master.Where(x => x.ID == 14)
                .SelectMany(y => y.PFO) 
                .SelectMany(z => z.Folio)
                .SelectMany(a => a.Subfolio)
                .Where(b=>b.Ind==32);

我可以为每个slave做同样的事情并将结果与Master查询结合起来，但有一种方法可以在一个linq操作中执行此操作。目前我正在使用一大堆foreach循环，非常笨重。

简化的类结构是：

Devices
  Master
    Portfolio
      Folio
         Subfolio
         Subfolio
      Folio
         Subfolio
         Subfolio
         Subfolio   
    Portfolio
      Folio
         Subfolio
         Subfolio
      Folio
         Subfolio
         Subfolio
         Subfolio
  Slave
     Portfolio
       Folio
         Subfolio
         Subfolio
       Folio
         Subfolio
         Subfolio
         Subfolio   
     Portfolio
       Folio
         Subfolio
         Subfolio
       Folio
         Subfolio
         Subfolio
         Subfolio
  Slave
     Portfolio
       Folio
         Subfolio
         Subfolio
       Folio
         Subfolio
         Subfolio
         Subfolio   
      Portfolio
       Folio
         Subfolio
         Subfolio
       Folio
         Subfolio
         Subfolio
         Subfolio

Answer 1

不确定此代码是否可行（测试需要时间），但是这样的事情应该可以解决问题：

var resultMaster = devices.Master.SelectMany(y => y.PFO);
var resultSlave = devices.Slave.SelectMany(y => y.PFO);
var result = resultMaster.Union(resultSlave)
                         .SelectMany(z => z.Folio)
                         .SelectMany(a => a.Subfolio)
                         .Where(b=>b.Ind==32);

可读性有3个部分，但查询将作为一个执行。

Answer 2

除此之外，这是我的完整解决方案（我没有说明Slaves是Masters的子类）

 public nF GetValuebyuNidIndex(dev devices, UInt32 MuNID, ushort nFIndex)
    {
        var result_m = devices.wNode.Where(p => p.uNID == MuNID)
        .SelectMany(x => x.PFO);
        var result_s = devices.wNode.Where(p => p.uNID == MuNID)
        .SelectMany(x => x.sNode)
            .SelectMany(x => x.PFO);
        var combined = result_m.Union(result_s)
            .SelectMany(x => x.Folio)
            .SelectMany(x => x.nF)
            .Where(x => x.Ind == nFIndex);

        return combined.FirstOrDefault();
     }

这也有效。据推测，它编译成同样的东西？

  public nF GetValuebyuNidIndex1(dev devices, UInt32 MuNID, ushort nFIndex)
    {
        var result_m = from dd in devices.wNode
                       where dd.uNID == MuNID
                       from pfo in dd.PFO
                       select pfo;
        var result_s = from dd in devices.wNode
                       where dd.uNID == MuNID
                       from snode in dd.sNode
                       from pfo in snode.PFO
                       select pfo;
        var combined = result_m.Union(result_s);
        var result = from cc in combined
                     from ff in cc.Folio
                     from nn in ff.nF
                     where nn.Ind == nFIndex
                     select nn;
        return result.FirstOrDefault();
    }

C＃Linq查询展平多级类

2 个答案: