Question

I have a class that uses linq to access the database. Some methods call others. For example:

class UserManager
{
   public User[] getList()
   {
       using(var db = new MyContext())
       {
             return db.Users.Where(item => item.Active == false);
       }
    }
    public User[] addUser(string name)
    {
       using(var db = new MyContext())
       {
           db.Users.InsertOnSubmit(new User() { id = Guid.NewId(),  name = name, active = false ...});
       }
       return getList();
    }

…

In the call to addUser I am required to return the new list. (I know as it stands it isn’t a great design, but I have eliminated detail for simplicity.) However, the call to getList creates a second data context.

I could pad this out with extra methods, viz:

public getList()
{
     using(var db = new MyContext())
        return getList(db);
}
public getList(MyContext db)
{
      ...
}

Then replace my call in addUser so as to keep the same data context.

I seem to see this type of thing a lot in my code, and I am concerned with the cost of creating and releasing all these data contexts. Does anyone have an opinion as to whether it is worthwhile putting in the extra work to eliminate the creation and deletion of these contexts?

Answer 1

Microsoft provides the following advice/recommendation to not reuse DataContext instances http://msdn.microsoft.com/en-us/library/bb386929.aspx

Frequently Asked Questions (LINQ to SQL)

Connection Pooling

Q. Is there a construct that can help
with DataContext pooling?

A. Do not try to reuse instances of
DataContext. Each DataContext
maintains state (including an identity
cache) for one particular edit/query
session. To obtain new instances based
on the current state of the database,
use a new DataContext.

You can still use underlying ADO.NET
connection pooling. For more
information, see SQL Server Connection
Pooling (ADO.NET).