什么时候需要配置数据库连接

Question

I have a class that contains several common methods customized for use in my MVC app, that I use in several places. Here is an example of some:

    private MyEntities db = new MyEntities();


    public List<SelectListItem> GetLocationList()
    {
        var query =
                db.v_LocationsAlphabetical.OrderByDescending(x => x.Category).ThenBy(x => x.LocationName).ToList()
                .Select(x => new SelectListItem
                {
                    Value = x.LocationID.ToString(),
                    Text = x.LocationName
                });

        return (query).ToList();
    }

    public IEnumerable<SelectListItem> GetStates()
    {
        var query = db.States.Select(x => new SelectListItem
        {
            Value = x.Abbr,
            Text = x.Name
        });

        return(query);
    }

    public List<Person> GetPeople()
    {
        var query = db.Person.OrderBy(m => m.LastName).ThenBy(m => m.FirstName).ToList();

        return (query);

    }

Each one of these methods makes a call to the database to get data and I was wondering if I need to add a dispose to each method. If not, why? Thanks.

Answer 1

You shouldn't call dispose in each method, because the lifetime of db is the same as that of the enclosing class since it's not a local variable in a method.

The typical way to handle this is to make the current class IDisposable and call db.Dispose() in the Dispose() method.

Answer 2

No. DbContexts don't have to be manually disposed, unless you manually manage the connection yourself. Therefore, disposing them is usually optional.

Answer 3

There are multiple ways of handling db connection in .NET
One of my favorites is the one called one dbcontext per request , which basically means you initialize your dbcontext when needed, do the work without thinking about instantiating or disposing, and dispose automatically when the request is done. (kinda UnitOfWork-ish)

I've already shown this approach here . It's not only applicable to EF, but to Linq2SQL, ADO.NET, etc. as well.