Question

public string Studentbyteacher(long _id)
{
    using (var context = new DbContext())
    {
        var studentID = (context.TeacherStudent.Where(x => x.TeacherID == _id).Select(x => x.studentID));
        foreach (var id in studentID)
        {
            var strJSON = JsonConvert.SerializeObject(context.Student.Where(x => x.ID == id).ToList());
            return strJSON;
        }
        return null;
    }
}

注意：我在数组列表中获得学生ID，如[0] 1，[1] 2，[2] 3 ......等等。所以我想根据ID返回学生的详细信息。如果我错了，请纠正我。

Answer 1

我认为您正在寻找可用于在循环中返回IEnumerable< T >或IEnumerable的收益率回报。

首先，您需要将方法更改为：

 public IEnumerable<string> Studentbyteacher(long _id)

并更改行

var strJSON = JsonConvert.SerializeObject(context.Student.Where(x => x.ID == id).ToList());

到

yield return JsonConvert.SerializeObject(context.Student.Where(x => x.ID == id).FirstOrDefault());

最后删除return strJson;

Answer 2

public string Studentbyteacher(long teacherId)
{
    using (var context = new DbContext())
    {
        var students = 
            from teacherStudent in context.TeacherStudent.Where(x => x.TeacherID == teacherId)
            let studentId = teacherStudent.studentID
            let student = context.Student.Where(x => x.ID == studentId).Single()
            select student;

        return JsonConvert.SerializeObject(students);
    }
}

使用foreach返回列表

2 个答案: