需要帮助将SQL查询编写为linq表达式

Question

我是新来的，所以如果我犯了任何错误，我会道歉。我编写了以下SQL代码来检索特定教师中每个用户提交的数量。

declare @faculty as int = 1
SELECT COUNT(ew_student.sName) AS Submissions, ew_student.sEmail, ew_faculty.nFaculty
FROM ew_student 
INNER JOIN ew_submission ON ew_student.sId = ew_submission.sId INNER JOIN
                            ew_faculty ON ew_student.sFaculty = ew_faculty.fId
WHERE ew_faculty.fId = @faculty
GROUP BY ew_student.sEmail, ew_faculty.nFaculty

通过MS SQL Server Management运行此查询会返回我期望的结果，但是在我的ASP.NET Web应用程序中，我在编写LINQ表达式时遇到了困难。

我的数据库上下文称为“db”。这是我到目前为止所得到的，但它返回了错误的结果。

var stats = from ew_submissions in db.ew_submissions
            where ew_submissions.ew_student.ew_faculty.fId == facultyId
            group new { ew_submissions.ew_student, ew_submissions.ew_student.ew_faculty } by new
            {
                ew_submissions.ew_student.sEmail,
                ew_submissions.ew_student.sName,
                ew_submissions.ew_student.ew_faculty.nFaculty

            } into g
            select new
            {
                Submissions = g.Count(),
                g.Key.sName


            };

return stats.ToList();

我想检索特定用户提交的提交数量，但上面的LINQ表达式总是为每个用户返回1。

Answer 1

您切换了要分组的位置（值）和按键（键）：

var stats = from ew_submissions in db.ew_submissions
            where ew_submissions.ew_student.ew_faculty.fId == facultyId
            group ew_submissions.ew_student.sName by new
            {
                ew_submissions.ew_student.sEmail,
                ew_submissions.ew_student.ew_faculty.nFaculty
            } into g
            select new
            {
                Submissions = g.Count(),
                g.Key.sName
            };

return stats.ToList();

另请注意，当您按sEmail和nFaculty进行分组时，您不希望也按sName进行分组，因为这样您可能会获得许多计数结果。