Linq 在多个表上按年份获取历史详细信息

Question

在我的应用程序中，我想显示给定用户的历史详细信息。一个用户可以有很多工作，并且可以使用不同的角色访问不同的促销活动。

我希望能够展示这种历史

年份        职位 促销

2012        助理 2012年促销

2013        经理 2013年促销

我试过这个查询（我正在使用 Linq 到实体）

var query = (from u in context.Users
             join j in context.Jobs.Where(jo => jo.JobStartDate.HasValue) on u.UserID equals j.UserID into jobs
             from job in jobs.DefaultIfEmpty()
             join uir in context.UserInRoles on u.UserID equals uir.UserID into userInRoles
             from userInRole in userInRoles.DefaultIfEmpty()
             join rip in context.RoleInPromotion on userInRole.RoleInPromotionID equals rip.RoleInPromotionID into roleInPromotions
             from roleInPromotion in roleInPromotions.DefaultIfEmpty()
             join p in context.Promotions.Where(pro => pro.PromotionStartDate.HasValue) on roleInPromotion.PromotionID equals p.PopulationTargetID into promotions
             from promo in promotions.DefaultIfEmpty()
             where u.UserID == userId 
             select new
             {
                 Year = job.JobStartDate.HasValue ? job.JobStartDate.Value.Year : promo.PromotionStartDate.HasValue ? promo.PromotionStartDate.Value.Year : 0,
                 JobTitle = job.JobTitle,
                 Promotion = promo.PromotionName
             }).Distinct().ToList();

但这给了我这个结果，即使用户在 2012 年无法访问任何促销活动

年份        职位 促销

2012        助理 2013年促销

2013        经理 2013年促销

我也试过了，但似乎没有任何改变

group new { job, promo } by new { jobYear = job.JobStartDate.Value.Year, promoYear = promo.PromotionStartDate.Value.Year } into grp

Answer 1

你试过这个吗：

var query = (from u in context.Users
             join j in context.Jobs.Where(jo => jo.JobStartDate.HasValue) on u.UserID equals j.UserID into jobs
             from job in jobs.DefaultIfEmpty()
             join uir in context.UserInRoles on u.UserID equals uir.UserID into userInRoles
             from userInRole in userInRoles.DefaultIfEmpty()
             join rip in context.RoleInPromotion on userInRole.RoleInPromotionID equals rip.RoleInPromotionID into roleInPromotions
             from roleInPromotion in roleInPromotions.DefaultIfEmpty()
             join p in context.Promotions.Where(pro => pro.PromotionStartDate.HasValue) on roleInPromotion.PromotionID equals p.PopulationTargetID into promotions
             from promo in promotions.DefaultIfEmpty()
             where u.UserID == userId 
         let year=job.JobStartDate.HasValue ? job.JobStartDate.Value.Year : promo.PromotionStartDate.HasValue ? promo.PromotionStartDate.Value.Year : 0
             select new
             {
                 Year =year ,
                 JobTitle = job.JobTitle,
                 Promotion = "Promotion "+year
             }).Distinct().ToList();