c# - 如何从复杂的 SQL 创建 LINQ？

Question

我有这个 SQL 查询:

 SELECT D.ID
 FROM Documents AS D
 INNER JOIN DocClasses AS DC WITH (NOLOCK) 
 ON D.DocClass = DC.ID
 INNER JOIN DocSubClasses AS DSC WITH (NOLOCK) 
 ON D.DocSubClass = DSC.ID AND DSC.DocClassID = DC.ID
 INNER JOIN DocPathFolders AS F WITH (NOLOCK) 
 ON D.DocPathFolderID = F.ID
 WHERE 
    DC.ShortName = 'PAY' AND DSC.Name = 'xxxxx' 
    AND UPPER(F.Description) = 'READY TO SEND'

我正在尝试将此查询转换为 LINQ。这是我到目前为止所做的:

 from D in ctx.Documents
 join DC in ctx.DocClasses on D.DocClass equals DC.ID
 join DSC in ctx.DocSubClasses 
     on new { D.DocSubClass, DSC.DocClassID } equals new { DSC.ID, DC.ID }
 join F in ctx.DocPathFolders 
     on D.DocPathFolderID equals F.ID
 where 
     DC.ShortName == "PAY" 
     && DSC.Name == "xxxxx" 
     && (F.Description).ToUpper() == "READY TO SEND"
 select D.ID;

我在这一行中遇到错误:

join DSC in ctx.DocSubClasses on new { D.DocSubClass, DSC.DocClassID } equals new { DSC.ID, DC.ID }

在这里，我遇到了以下错误:

The name 'DSC' is not in scope on the left side of 'equals'

The name 'DC' is not in scope on the right side of 'equals'

我是 LINQ 的新手，这就是我无法解决这些错误的原因。我会感谢以上任何建议。谢谢。

Answer 1

您应该像这样重新排列匿名对象中的属性:

join DSC in ctx.DocSubClasses 
on new { D.DocSubClass, DC.ID } equals new { DSC.DocClassID, DSC.ID }

右边的应该是你正在加入的表(DSC)，左边的可以是之前的表