Linq DataContext - Where does it go in a class? - asp.net

Question

I'm still new to LINQ and am having some issues in knowing where to put a DataContext in a Class.
Here's what I've tried:
public class Student
{
private static LinqClassesDataContext db = new LinqClassesDataContext();
public static Profile GetProfile(int uID)
{
var profile = (from p in db.Profiles
where p.uID == uID
select p).FirstOrDefault();
return profile;
}
}
But I'm having issues of the result caching(?) - see this issue: Weird caching issue with ASP.net/Linq
Then, I tried putting the DataContext in each of the methods in the class:
public class Student
{
public static Profile GetProfile(int uID)
{
using (LinqClassesDataContext db = new LinqClassesDataContext())
{
var profile = (from p in db.Profiles
where p.uID == uID
select p).FirstOrDefault();
return profile;
}
}
}
But then I was getting a “DataContext accessed after Dispose” error in my application.
So, the only other way that I've seen this done is this way:
public class Student
{
public static Profile GetProfile(int uID)
{
LinqClassesDataContext db = new LinqClassesDataContext();
{
var profile = (from p in db.Profiles
where p.uID == uID
select p).FirstOrDefault();
return profile;
}
}
}
But it seems that this isn't the most efficient way. Perhaps I'm using Linq incorrectly (I'm a self taught ASP.net'er), but can someone enlighten me on what the best way to move forward?

Answer 1

Objects are attached to the context, so as soon as you dispose it, if you try to navigate it's relationships, you will get these kinds of errors as you got with option #2.
Since ASP.NET is stateless, you need to either load the profile object every time it's needed, and not cache the object statically, or load the object and all of it's related data using the DataLoadOptions object of LINQ to SQL (see this). That way, you shouldn't need the context when accessing related data sets.
As far as where to put it, I always put it in HttpContext.Current.Items collection, which can store the instance per request, and then share it from here across all requests. I wrap some code around it so my application doesn't know that it's getting it from here. However, you have to be careful, because if a process outside of ASP.NET uses the same code, this approach blows up because there is no HTTP context. In that case, instantiate the context every time.