entity frameworkjoin3个表

我想join三张桌子，但是我不明白这个方法…

我完成了连接2个表格

var entryPoint = dbContext.tbl_EntryPoint .Join(dbContext.tbl_Entry, c => c.EID, cm => cm.EID, (c, cm) => new { UID = cm.OwnerUID, TID = cm.TID, EID = c.EID, }). Where(a => a.UID == user.UID).Take(10); 

我想用TID PK包含tbl_Title表并获得Title字段。

非常感谢

Answer 1

我认为使用基于语法的查询会更容易：

 var entryPoint = (from ep in dbContext.tbl_EntryPoint join e in dbContext.tbl_Entry on ep.EID equals e.EID join t in dbContext.tbl_Title on e.TID equals t.TID where e.OwnerID == user.UID select new { UID = e.OwnerID, TID = e.TID, Title = t.Title, EID = e.EID }).Take(10); 

您应该添加orderby子句，以确保Top(10)返回正确的前十个项目。

Answer 2

这是未经testing的，但我相信这个语法应该适用于lambda查询。 当你用这个语法连接更多的表时，你必须深入到新的对象中去达到你想要处理的值。

 var fullEntries = dbContext.tbl_EntryPoint .Join( dbContext.tbl_Entry, entryPoint => entryPoint.EID, entry => entry.EID, (entryPoint, entry) => new { entryPoint, entry } ) .Join( dbContext.tbl_Title, combinedEntry => combinedEntry.entry.TID, title => title.TID, (combinedEntry, title) => new { UID = combinedEntry.entry.OwnerUID, TID = combinedEntry.entry.TID, EID = combinedEntry.entryPoint.EID, Title = title.Title } ) .Where(fullEntry => fullEntry.UID == user.UID) .Take(10); 

Answer 3

 var entryPoint = (from ep in dbContext.tbl_EntryPoint join e in dbContext.tbl_Entry on ep.EID equals e.EID join t in dbContext.tbl_Title on e.TID equals t.TID where e.OwnerID == user.UID select new { UID = e.OwnerID, TID = e.TID, Title = t.Title, EID = e.EID }).Take(10); Great answer