Question

http://msdn.microsoft.com/en-us/library/dd742359.aspx中的

描述了关系多对多数据关系。

现在如何在CourseInstructo上执行插入，删除和更新？

对于一对一的关系我这样做：

var  context= new Modle2();
var course= new Course() {title="math",...};
context.Course.addObject(course);
context.SaveChanges()

Answer 1

您可以在任一端使用导航属性来操纵多对多关系。例如，

using (var context = new Model2())
{
    int courseID = 4022;
    var course = (from c in context.Courses
                 where c.CourseID == courseID
                 select c).First();

    int personID = 17;
    var instructor = (from p in context.Person
                  where p.PersonID == personID
                  select p).First();

    course.Person.Add(instructor);
    // alternatively, this will also do - instructor.Course.Add(course);
    context.SaveChanges();
}

要删除，请使用类似的逻辑 - 例如，

using (var context = new Model2())
{
    int courseID = 4022;
    var course = (from c in context.Courses
                 where c.CourseID == courseID
                 select c).First();

    int personID = 17;
    var instructor = (from p in context.Person
                  where p.PersonID == personID
                  select p).First();

    course.Person.Remove(instructor);
    context.SaveChanges();
}

更新对于多对多关系没有意义 - 它实质上是添加和删除组合。

插入，删除，更新（关系多对多）

1 个答案: