C# 如果第二个或第三个表为空，LINQ Join不返回结果

我有三张桌子：

Module_Articles_Articles
Module_Articles_Categories
Module_Articles_Comments

我想在repeater my query中显示我的文章：

var articles =
                (from a in context.Module_Articles_Articles
                 join c in context.Module_Articles_Categories on a.CategoryID equals c.CategoryID
                 join co in context.Module_Articles_Comments on a.ArticleID equals co.ArticleID
                 where a.IsDraft == false
                 orderby a.ArticleID descending
                 select new
                 {
                     a.ArticleID,
                     a.ArticleTitle,
                     a.ArticleContent,
                     a.Image,
                     a.Sender,
                     a.SentDate,
                     a.Summary,
                     a.Likes,
                     a.Dislikes,
                     a.Tags,
                     a.PostMode,
                     c.CategoryID,
                     c.CategoryTitle,
                     AcceptedCommentsCount = 
                     (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID && com.Status select com)
                     .Count(),
                     DeniedCommentsCount =
                     (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID 
                          && com.Status == false select com)
                     .Count()
                 }).ToList();

但是当

Module\u Articles\u Categories

或

Module\u Articles\u Comments

为空时，我的查询不会返回任何结果！

---

我的代码是真的吗？如果没有，我该怎么做？

您想要一个OUTTER连接，这可以通过添加

.DefaultIfEmpty（）

---

您没有得到结果，因为LINQ连接导致

内部连接

s。您可能需要

LEFT JOIN

s。按以下步骤做

var articles =
    (from a in context.Module_Articles_Articles
     join c in context.Module_Articles_Categories on a.CategoryID equals c.CategoryID into joinTable1
     from c in joinTable1.DefaultIfEmpty()
     join co in context.Module_Articles_Comments on a.ArticleID equals co.ArticleID into joinTable2
     from co in joinTable2.DefaultIfEmpty()
     where a.IsDraft == false
     orderby a.ArticleID descending
     select new
     {
         a.ArticleID,
         a.ArticleTitle,
         a.ArticleContent,
         a.Image,
         a.Sender,
         a.SentDate,
         a.Summary,
         a.Likes,
         a.Dislikes,
         a.Tags,
         a.PostMode,
         c.CategoryID,
         c.CategoryTitle,
         AcceptedCommentsCount = 
         (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID && com.Status select com)
         .Count(),
         DeniedCommentsCount =
         (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID 
              && com.Status == false select com)
         .Count()
     }).ToList();

---

我想你需要在你的问题中添加

LINQ

标记，以获得快速答案。谢谢@sudhakartrapudi，补充。我将你的标题更新为问题，以前没有任何信息……非常感谢@ScottSelbystep通过代码，当断点到达这一行时，它将变成SQL语句（假设你使用SQL Server）然后直接在数据库中运行sql，看看它是否返回结果，或者实际发布生成的sql如何获取生成的sql语法？好的，实际上我刚刚更新了代码，出现了一些语法错误，现在试试，然后我将告诉您如何获取生成的sql

var articles =
    (from a in context.Module_Articles_Articles
     join c in context.Module_Articles_Categories on a.CategoryID equals c.CategoryID into joinTable1
     from c in joinTable1.DefaultIfEmpty()
     join co in context.Module_Articles_Comments on a.ArticleID equals co.ArticleID into joinTable2
     from co in joinTable2.DefaultIfEmpty()
     where a.IsDraft == false
     orderby a.ArticleID descending
     select new
     {
         a.ArticleID,
         a.ArticleTitle,
         a.ArticleContent,
         a.Image,
         a.Sender,
         a.SentDate,
         a.Summary,
         a.Likes,
         a.Dislikes,
         a.Tags,
         a.PostMode,
         c.CategoryID,
         c.CategoryTitle,
         AcceptedCommentsCount = 
         (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID && com.Status select com)
         .Count(),
         DeniedCommentsCount =
         (from com in context.Module_Articles_Comments where com.ArticleID == a.ArticleID 
              && com.Status == false select com)
         .Count()
     }).ToList();