C# 如何使用unioan和linq中的嵌套？

如何将sql转换为linq。我不理解嵌套选择查询。我需要linq代码。请帮助我：((((

林克：

如果我写上述代码，错误如下：

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这适合你的需要吗

var id = 
  (from task in stock.CTasks select new { task.id, task.workorder, jobseqno= task.jobseqno } )
  .Union(from card in stock.NonRoutineCards select new { card.id, card.workorderno, jobseqno = card.cardno })
  .Union(from card in stock.AdditionalWorkCards select new { card.id, card.workorderno, jobseqno = card.cardno })
  .Where(x => x.workorderno.TrimEnd() == ToNo && x.jobseqno == ToSeq)
  .FirstOrDefault();

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SQL代码将多个表连接在一起：您还应该对UNION ALL进行一些特定的读取，不知道它是什么，但它必须是某种连接。我添加了一个图片和linq查询，这是因为您的一个字段名为“jobseqno”，而另一个子查询中的同一个字段名为“cardno”。在这两种情况下都显式指定字段名：…new{task.ID，task.workorderno，Num=（int）task.jobseqno}…新的{card.ID，card.workorderno，Num=card.cardno}…其中（…x.Num==ToSeq）我刚才在前面的评论中告诉过你：）

  var id = 
  (from task in stock.CTasks select new { task.id, task.workorder, task.jobseqno } )
  .Union(from card in stock.NonRoutineCards select new { card.id, card.workorderno, card.cardno })
  .Union(from card in stock.AdditionalWorkCards select new { card.id, card.workorderno, card.cardno })
  .Where(x => x.workorderno.TrimEnd() == ToNo && x.jobseqno == ToSeq)
  .FirstOrDefault();

var id = 
  (from task in stock.CTasks select new { task.id, task.workorder, jobseqno= task.jobseqno } )
  .Union(from card in stock.NonRoutineCards select new { card.id, card.workorderno, jobseqno = card.cardno })
  .Union(from card in stock.AdditionalWorkCards select new { card.id, card.workorderno, jobseqno = card.cardno })
  .Where(x => x.workorderno.TrimEnd() == ToNo && x.jobseqno == ToSeq)
  .FirstOrDefault();