Question

我将实体框架与点网框架一起使用

例如，我有像

这样的学生班

public class Student
{
    public int StudentId { get; set; }
    public int Age { get; set; }
    public int DepartmentId { get; set; }
    public string Name { get; set; }
}

当我需要在许多系中寻找学生时，我可以像下面这样

List<Student> students = new List<Student>
{
    new Student{Age = 12,DepartmentId =1 },
    new Student{Age = 11,DepartmentId =2 },
    new Student{Age = 11,DepartmentId =3 },
    new Student{Age = 13,DepartmentId =4 },
};
// get all department ids
var departmentIds = students.Select(s => s.DepartmentId);
var studentList = DbContext.Students.Where(s=>departmentIds.Contains(s.DepartmentId)).ToList();

这将生成类似SQL查询

  Select StudentId , Age , DepartmentId , Name
  From Students where DepartmentId in (1 , 2 , 3 , 4)

我的问题

我需要搜索与学生列表中的任何项目匹配的任何学生类似于以下查询

Select StudentId , Age , DepartmentId , Name
From students 
Where 
    (departmentId= 1  and age = 12)
    OR
    (departmentId= 2  and age = 11)
    OR
    (departmentId= 3  and age = 12)
    OR
    (departmentId= 4  and age = 13)

Answer 1

存储每个部门的年龄并写

var departmentAge = departments.ToDictionary(d => d.DepartmentId, d => d.RequiredAge);

然后

.Where(s => departmentIds.Contains(s.DepartmentId) && s.Age == departmentAge[s.DepartmentId])

第二部分不可翻译为SQL。您可能需要用AsEnumerable分隔它，或将查询中的两个表连接起来以获得类似的信息

Select s.StudentId, s.Age, s.DepartmentId, s.Name
From Students s inner join Departments d
where s.DepartmentId in (1 , 2 , 3 , 4) and s.Age = d.RequiredAge

Answer 2

根据Henk Holterman的评论，只需将其写出

List<Student> students = new List<Student>
{
    new Student{Age = 12,DepartmentId =1 },
    new Student{Age = 11,DepartmentId =2 },
    new Student{Age = 11,DepartmentId =3 },
    new Student{Age = 13,DepartmentId =4 },
};

var studentList = DbContext.Students.Where(s=> (s.DepartmentId == students[0] && 
                s.Age == students[0]) || (s.DepartmentId == students[1] && s.Age == 
                students[1]) || (s.DepartmentId == students[2] && s.Age == 
                students[2]) || (s.DepartmentId == students[3] && s.Age == 
                students[3])).ToList();

Linq查询过滤器，其“包含”具有list <T>多个属性

2 个答案: