linq中如何在join中指定多个条件
public ActionResult Edit(int id) { using (DataContext db = new DataContext(ConfigurationManager.ConnectionStrings["sqlConnection"].ConnectionString)) { IQueryable<ClassInformation> result = from c in db.GetTable<TClass>() join t in db.GetTable<TTeacher>() on new { id = c.ID, id1 = c.ID } equals new { id = t.ClassID, id1 = id } select new ClassInformation { ID = c.ID, ClassID = t.ClassID, Name = c.Name, TeacherName = t.Name, Address = t.Address, Phone = t.Phone, Email = t.Email }; ClassInformation k = result.Single(); ViewData["K"] = k; return View(); } }
借助于匿名类型:其实和解决按多条件分组的思路是一样的。
var a = from m in DbContext.Set<T1>() join q in DbContext.Set<T2>() on new { m.ID, Phone=m.Phone1 } equals new { q.ID, Phone=q.Phone2 } where m.Phone1 !=null select new { m.ID, m.Phone1 }; a = a.OrderBy(m => m.Phone1).Skip(2).Take(2);
SELECT [Extent1].[ID] AS [ID], [Extent1].[Phone1] AS [Phone1], AS [C1] FROM [dbo].[T1] AS [Extent1] INNER JOIN [dbo].[T2] AS [Extent2] ON ([Extent1].[ID] = [Extent2].[ID]) AND (([Extent1].[Phone1] = [Extent2].[Phone2]) OR (([Extent1].[Phone1] IS NULL) AND ([Extent2].[Phone2] IS NULL))) WHERE [Extent1].[Phone1] IS NOT NULL
所以linq为什么要这么写,看到生成的sql语句 就不言而喻了,因为linq多管闲事的将NULL给总结进去了
本文来自博客园,作者:willamyao,转载请注明原文链接:https://www.cnblogs.com/robertyao/p/11136559.html
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