3

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，我收到以下错误：

名称“DSC”不在“等于”左侧的范围内

名称“DC”不在“等于”右侧的范围内

我是 LINQ 的新手，这就是我无法解决这些错误的原因。我会对上述内容提出任何建议。谢谢。

4

5 回答 5

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 }

右边的应该是你要加入的表（DSC），左边的可以是以前的表

于 2018-07-04T14:22:55.953 回答
1

您可以尝试使用Lambda Join而不是使用LINQ.

您的JOIN陈述如下所示Lambda。

C#小提琴

var result = ctx.Documents.Join(ctx.DocClasses , d => new { Id = d.DocClass }, dc => new { Id = dc.ID }, (d, dc) => new { doc = d, docClass = dc }) //INNER JOIN DocClasses  
                          .Join(ctx.DocSubClasses , d => new { sc = d.doc.DocSubClass, Id = d.docClass.ID }, dsc => new { sc = dsc.ID, Id = dsc.DocClassID }, (d, dsc) => new { doc = d, dsc = dsc } ) //INNER JOIN DocSubClasses
                          .Join(ctx.DocPathFolders, d => new { fId = d.doc.doc.DocPathFolderID }, f => new { fId = f.ID }, (d, f) => new { doc = d, f = f }) //INNER JOIN DocPathFolders
                          .Where(x => x.doc.doc.docClass.ShortName == "PAY" && x.doc.dsc.Name == "xxxxx" && x.f.Description.ToUpper() == "READY TO SEND")//Apply where clause
                          .Select(y => y.doc.doc.doc.ID);//Select whatever you want
于 2018-07-04T14:54:44.003 回答
0

这是我解决问题的方法：

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, DC.ID } equals new { DocSubClass = DSC.ID, ID = DSC.DocClassID }
join F in ctx.DocPathFolders on D.DocPathFolderID equals F.ID
where DC.ShortName == "PAY" && DSC.Name == "xxxx" && (F.Description).ToUpper() == "READY TO SEND"
select D.ID;
于 2018-07-04T14:22:50.087 回答
0

只需将 DSC 切换到 equals 的右侧，DC 切换到左侧，它应该可以正常工作。

join DSC in ctx.DocSubClasses on new { D.DocSubClass, DC.ID } equals new { DSC.ID, DSC.DocClassID}
于 2018-07-04T14:27:26.623 回答
0

提示：如果您在数据库中适当地设置了关系，您几乎不需要使用“join”。在 LINQ 中编写更容易，并且关系被公开为“导航属性”。您只需使用“点符号”。IE：

var result = from d in ctx.Documents
           where d.DocClasses.Any( dc => dc.ShortName == "PAY" 
              && dc.DocSubClasses.Any( dsc => dsc.Name == "xxxxx" )
              && d.DocPathFolders.Any( dpf => dpf.Description.ToUpper() == "READY TO SEND" )
            select d.ID;

注意：我们对您的模型没有任何想法。我假设关系是一对多。如果它是多对一，那么您只需使用如下符号：

where d.DocClass.ShortName == "PAY" 
                  && d.DocClass.DocSubClass.Name == "xxxxx" 
                  && d.DocPathFolder.Description.ToUpper() == "READY TO SEND"

提示 2：从 LinqPad.net 下载并开始使用 Linqpad。这是一个很棒的工具，您不仅可以测试您的 LINQ 查询，还可以用作 .Net 便签本。

于 2018-07-04T14:30:37.640 回答