Using statements in a web api - asp.net-mvc

Question

I found this code here
using (var objCtx = new SchoolDBEntities())
{
var schoolCourse = from cs in objCtx.Courses
where cs.CourseName == "Course1"
select cs;
Course mathCourse = schoolCourse.FirstOrDefault<Course>();
IList<Course> courseList = schoolCourse.ToList<Course>();
string courseName = mathCourse.CourseName;
}
And I am using it in a Get method of a web api. When i use a using statement I get the following error
The ObjectContext instance has been disposed and can no longer be used for operations that require a connection
I I do not use it, then how would I dispose of the context object responsibly?

Answer 1

I use something like this to solve the problem without resorting to eager loading (in fact usually in a generic abstract base controller that I extend, but this example is simplified):
public class MyController : ApiController
{
private SchoolDBEntities _objCtx;
// Singleton ObjectContext
protected SchoolDBEntities objCtx
{
if(_objCtx == null) _objCtx = new SchoolDBEntities();
return _objCtx;
}
// Use singleton objCtx without using wrapper here, in Get() or other methods.
public String Get()
{
var schoolCourse = from cs in objCtx.Courses
where cs.CourseName == "Course1"
select cs;
Course mathCourse = schoolCourse.FirstOrDefault<Course>();
string courseName = mathCourse.CourseName;
return courseName
}
// ApiController implements IDisposable, so you can override Dispose to do clean-up here.
// This is not called until the controller is disposed, so you won't get the error you report.
protected override void Dispose(Boolean disposing)
{
if (_objCtx!= null)
{
_objCtx.Dispose();
_objCtx = null;
}
base.Dispose(disposing);
}
}