Disposing of object context in entity framework 4

Question

I have an entity class which is auto generated from my database model. This class inherits the ObjectContext which inturn inherits IDisposable.

I have created a repository that has various methods which use a single instance of the entity object to interact with the database.

Auto generated class

public partial class DevEntities : ObjectContext
{
    public const string ConnectionString = "name=DevEntities";
    public const string ContainerName = "DevEntities";

Repository Class

DevEntities db = new DevEntities();

        public Customer GetCustomerByID(int id)
    {
        var customers = db.Customers.FirstOrDefault(c => c.CustomerId == id);

        return customers;
    }

    public Customer GetCustomerByPasswordUsername(string email, string password)
    {
        var customers = db.Customers.FirstOrDefault(c => c.Email == email && c.Password == password);

        return customers;
    }

From this you can see that I make multiple references to the db instance. My question is, am I better to instantiate a new DevEntity within each method, thus being able to implement the using statement, and so ensure correct disposal, or is my current implementation ok?

Answer 1

I would implement IDisposable on the Repository class as well, so it can dispose the ObjectContext. If you return a different ObjectContext each time, you can run into problems when doing queries between those objects, as those are attached to different ObjectContexts, which will result in an exception.

Definition:

public class Repository : IDisposable
{
    DevEntities db = new DevEntities();

    public Customer GetCustomerByID(int id)
    {
        var customers = db.Customers.FirstOrDefault(c => c.CustomerId == id);

        return customers;
    }

    public Customer GetCustomerByPasswordUsername(string email, string password)
    {
        var customers = db.Customers.FirstOrDefault(c => c.Email == email && c.Password == password);

        return customers;
    }

    public void Dispose()
    {
        db.Dispose();
    }
}

Usage:

using(Repository r = new Repository())
{
  //do stuff with your repository
}

Doing this, your repository takes care of disposing the ObjectContext after you used it.