Linq Join Group by 时报Nullable object must have a value. 例如: from s in subject on ch.SubId equals s.SubId join gc in (from aq in question group aq by aq.ChapterId into gaq select new { Id = gaq.Key, Count = gaq.Count(), }) on s.QueId equals gc.Id into…

还是习惯先撸一段SQL * FROM User_Pic P AND P.Guid = R.UserPicGuid ORDER BY PicSize DESC 然后发现Linq中的join不能多条件... 结果找到解决方案如下 ; var pic = (from p in db.User_Pic join r in db.R_User_Pic on new { _guid = p.Guid, _id = ID } equals new { _guid = r.UserPicGuid, _id =…

MXS&Vincene  ─╄OvЁ  &0000022─╄OvЁ  MXS&Vincene MXS&Vincene  ─╄OvЁ:今天很残酷,明天更残酷,后天很美好,但是绝大部分人是死在明天晚上,只有那些真正的英雄才能见到后天的太阳. MXS&Vincene  ─╄OvЁ:We're here to put a dent in the universe. Otherwise why else even be here? 正文>>>>>…

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().Take(); SELECT…

代码: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using System.Reflection; namespace TestConsole { public class Program { public static void Main(string[] args) { var classify_list = new List…

1.sql语句: select * from Users u join Teachers t on u.UserID==t.TeacherID and u.Name=t.Name 2.linq写法: 1).方法一: 将多个字段的比较,new 一个对象进行比较: 注意:对象的属性名要保持一致: var userInfos = from u in db.Users join t in db.Teachers on new { u.UserID , u.Name } equals new { User…

内部联接 按照关系数据库的说法,“内部联接”产生一个结果集,对于该结果集内第一个集合中的每个元素,只要在第二个集合中存在一个匹配元素,该元素就会出现一次. 如果第一个集合中的某个元素没有匹配元素,则它不会出现在结果集内. Join 方法(通过 C# 中的 join 子句调用)可实现内联. 内部连接的4种变体: 简单联接,它基于一个简单的键将来自两个数据源的元素相互关联. 复合联接,它基于一个复合键将来自两个数据源的元素相互关联. 使用复合键(即由多个值组成的键)可以基于多个属性将元素相互关联.…

var query = _db.Bank_CommercialOpus .Join(_db.Bank_Opus, s => s.OpusID, Opus => Opus.ID, (s, Opus) => new { ID = s.ID, CompanyName = s.CompanyName, ChannelAddress = s.ChannelAddress, CpAddress = s.CpAddress, OpusID = s.OpusID, Oupsname = Opus.OpT…

from VS in m2db.Inf_VehicleSale join RS1 in m2db.His_RecSale on new { VS.vehicleCode, auctionCode=VS.AuctionCode } equals new { RS1.vehicleCode, RS1.auctionCode }…

单条件: var query = from person in people join pet in pets on person equals pet.Owner select new { OwnerName = person.FirstName, PetName = pet.Name }; 多条件: IEnumerable<string> query = from employee in employees join student in students on new { employe…