Question

我是SQL Server中使用EF6的ASP.NET MVC C＃的新手，我有3个表：

学生资讯
课程
Stud_Courses在学生和课程之间的映射

示例数据：

Cou_ID | Stud_ID
-------+--------
     1 | 1
     1 | 2

我想按学生姓名或课程名称在学生页面中进行搜索，例如，如果用户输入数学，则表示所有学生都需要数学我写了这个代码，按名称正确搜索问题是按照课程名称显示错误，在此行的s.Stud_ID

StuList = db.Students.Where(x => x.StudentId == s.Stud_ID).ToList();

（注意：Stud_ID类型是数据库中的varchar）

Stud_Courses不包含＆＃39; Stud_ID＆＃39;的定义没有扩展方法＆＃39; Stud_ID＆＃39;接受类型＆＃39; List＆＃39;的第一个参数。可以找到（你错过了使用指令或汇编引用

我的控制器代码

public JsonResult GetSearchingData(string SearchBy, string SearchValue){

List<Students> StuList = new List<Students>();

if (SearchBy == "Name")    
{
    StuList = db.Students.Where(x => x.StudentsName.Contains(SearchValue) || SearchValue == null).ToList();
    var subCategoryToReturn = SupList.Select(S => new { supervisorName = S.supervisorName });
    return Json(SupList, JsonRequestBehavior.AllowGet);   
}

if (SearchBy == "Course Name")
{
    var c = db.Courses.Where(x => x.CoursesName == SearchValue).SingleOrDefault();
    var CN = c.CourseId;
    var s = db.Stud_Courses.Where(x => x.Cou_ID == CN).ToList();
    StuList = db.Students.Where(x => x.StudentId == s.Stud_ID).ToList();  
    // here the error happens
    return Json(SupList, JsonRequestBehavior.AllowGet);}
}

Stud_Courses模型

namespace MyModel.Models{
using System;
using System.Collections.Generic;

public partial class Stud_Courses{
    public int Id { get; set; }
    public Nullable<int> Cou_ID { get; set; }
    public string Stud_Id { get; set; }

    public virtual Courses Courses{ get; set; }
    public virtual Student Student { get; set; }
}}

Answer 1

"s" is a List so you need to select the Stud_Id, so s will be a List. Then you can get all students that are contained in s.

var s = db.Stud_Courses.Where(x => x.Cou_ID == CN).Select(x => x.Stud_Id).ToList();
StuList = db.Students.Where(x => s.Contains(x.StudentId)).ToList();

or you can reduce the 3 separate queries to

StuList = db.Students.Where(x => x.Stud_Courses.Any(y => y.Courses.CoursesName == SearchValue)).ToList();

在多个表之间搜索功能

1 个答案: