實體框架 - 內連接到左連接

Question

美好的一天！我需要改變加入到左加入我的查詢 -

 var query = (from sections in context.Sections 
        join themes in context.Themes on sections.SectionId equals themes.SectionId 
        join comments in context.Comments on themes.ThemeId equals comments.ThemeId 
        select new { sections.SectionId, sections.SectionTitle, themes.ThemeId, comments.CommentId } into x 
        group x by new { x.SectionId, x.SectionTitle } into g 
        select new SectionInfo 
        { 
         SectionId = g.Key.SectionId, 
         SectionTitle = g.Key.SectionTitle, 
         ThemeCount = g.Select(s => s.ThemeId).Count(), 
         CommentCount = g.Select(s => s.CommentId).Count() 
        }).ToList(); 

- 拜託，我不知道（

Answer 1

您需要使用DefaultIfEmpty

一種方法是這樣的：

from themes in context.Themes.Where(x => sections.SectionId == x.SectionId) 
          .DefaultIfEmpty() 

---

替代方式

join themes in context.Themes on sections.SectionId equals themes.SectionId into themesGroup 
from themes in themesGroup.DefaultIfEmpty()