C# 对LINQ的SQL查询（使用带两个键的join）

我已经得到了SQL查询并尝试使用LINQ，因为如果EF。有人能看一下吗？请告诉我我的错在哪里？SQL查询正在工作，但LINQ不返回任何数据。基本上有两个表A和表B。我想连接A\B，即（使数据存在于表A中，但不存在于表B中）

我试过了，但没用。当我连接两个表时，需要两个键值相匹配，正如您从SQL表中看到的

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 };

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原始查询为左连接，而代码为内部查询，请将其更改为：

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 };

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尝试在连接中只放置一个键，修改的对象是两个项目（（course.CourseID==Blist.CourseID）&&（course.CourseID==training.CourseID））@AdilSari很乐意提供帮助！

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 };