SQL Query to LINQ（使用带有两个键的连接）

Question

我有 SQL Query 并尝试使用 LINQ，因为如果 EF.有人可以看看它告诉我我的错误在哪里，好吗？ SQL 查询正在运行，但 LINQ 不返回任何数据。基本上有两个表 A 和表 B。我想加入 A\B 即（带我数据存在于表 A 中但不在表 B 中）

SqlQueryText = "  SELECT A.EmployeeID" +
               "  FROM EmployeeCourseModels A " +
               "  LEFT JOIN EmployeeTrainingModels B " +
              "   ON A.EmployeeID = B.EmployeeID and a.CourseID = B.CourseID" +
              "   WHERE(B.CourseID is null and B.EmployeeID is null) AND A.CourseID = " + courseID;

我试过了，但没有用。从 SQL 表中可以看出，当我加入两个表时，我需要两个键值来匹配。

var ReqList = from course in employeeCourseRepository.EmployeeCourseList
              join training in employeeTrainingRepository.EmployeeTrainingList
              on new { c = course.CourseID, e = course.EmployeeID } equals new { c = training.CourseID, e = training.EmployeeID }
              where  (course.CourseID == Blist.CourseID)
                           select new  {  empID = course.EmployeeID };

Answer 1

您的原始查询是 LEFT JOIN 而您的代码是 INNER 之一，将其更改为：

var ReqList = from course in employeeCourseRepository.EmployeeCourseList.Where(c => c.CourseID == Blist.CourseID)
              join training in employeeTrainingRepository.EmployeeTrainingList
              on new { c = course.CourseID, e = course.EmployeeID } equals new { c = training.CourseID, e = training.EmployeeID } into j
              from res in j.DefaultIfEmpty()
              select new  {  empID = course.EmployeeID };