Question

我正在尝试加入2个 LINQ 查询。但是根据我的愿望，我没有得到结果。

List<TeacherSubjectVM> query = (from t in uow.staffs
                                join ts in uow.teachersubjects on t.ID equals ts.teacherID
                                join s in uow.subjects on ts.subjectID equals s.ID
                                select new TeacherSubjectVM
                                {
                                    subjectName = s.Name,
                                    teacherName = t.fname,
                                }).ToList();

List<TeacherSubjectVM> query1 = (from t in uow.subjects
                                 join ts in uow.classsubjects on t.ID equals ts.subjectID
                                 join s in uow.jamats on ts.subjectID equals s.ID
                                 select new TeacherSubjectVM
                                 {
                                     section = s.section,
                                     className = s.name,
                                 }).ToList();

List<TeacherSubjectVM> combine = query.Concat(query1).ToList();

班级名称和科目应与科目名称和教师姓名位于同一行：

Answer 1

只需一步即可加入您想要加入的所有表格：

List<TeacherSubjectVM> query = (from t in uow.staffs
                            join ts in uow.teachersubjects on t.ID equals ts.teacherID
                            join s in uow.subjects on ts.subjectID equals s.ID
                            join cs in uow.classsubjects on ts.subjectID equals cs.ID
                            join j in uow.jamats on ts.subjectID equals j.ID
                            select new TeacherSubjectVM
                            {
                                subjectName = s.Name,
                                teacherName = t.fname,
                                section = cs.section,
                                className = j.name,
                             }).ToList();

我认为你正在尝试做的事情，但是变量名称和变量名称的重复使用使得它很难阅读。

Answer 2

您正在采取的方法无法提供所需的方法，因为Concat函数不会合并对象，它只会将query1中的所有项目追加到query中列表，这里combine。

达到你的愿望是循环它们并手动合并对象，如下所示：

List<TeacherSubjectVM> query = (from t in uow.staffs
                                join ts in uow.teachersubjects on t.ID equals ts.teacherID
                                join s in uow.subjects on ts.subjectID equals s.ID
                                select new TeacherSubjectVM
                                {
                                    Id = ts.subjectID,
                                    subjectName = s.Name,
                                    teacherName = t.fname,
                                }).ToList();

List<TeacherSubjectVM> query1 = (from t in uow.subjects
                                 join ts in uow.classsubjects on t.ID equals ts.subjectID
                                 join s in uow.jamats on ts.subjectID equals s.ID
                                 select new TeacherSubjectVM
                                 {
                                     Id = ts.subjectID,
                                     section = s.section,
                                     className = s.name,
                                 }).ToList();

query.ForEach(item => {
    var otherItem = query1.Where(itm => itm.Id == item.Id).FirstOrDefault();

    item.subjectName = otherItem?.subjectName;
    item.teacherName = otherItem?.teacherName;
});

请注意，我将Id属性添加到TeacherSubjectVM类，以便可以对其进行合并，它应该用主题ID填充，因为它是两者之间唯一的共同点对象。

PS：使用描述性变量名称总是更好的做法，这有助于提高代码的可读性和可维护性：）

结合2个LINQ查询

2 个答案: