Question

in http://msdn.microsoft.com/en-us/library/dd742359.aspx described about relationship Many-to-Many data relationships.

now how can perform insert,delete,update on CourseInstructo؟

for one-to-man relation This way I do:

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

Answer 1

You can use navigation property at either end to manipulate the many-to-many relation.
For example,

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();
}

For removing, use similar logic – for example,

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();
}

Update does not make sense for many-to-many relations – it essentially Add and Remove combination.