Will my Unit of Work implementation cause memory leak? - entity-framework

Question

I implemented my repository pattern and unit of work in the following way:
How to create a simple data access layer
How to create unit of work
and I was asked if create multiple instance of my database (which is the unit of work) will cause memory leak? and what are the downside of such implementation? or is the implementation done right?
Thanks.

Answer 1

What you should worry about is the creation of the DbContext as this is expensive.
I typically use one DbContext per request instead of creating multiple DbContext instances everywhere.
I store it in the HttpContext object and dispose of it at the end of the request.
You can find more info on it here
Find below my modified implementation. (original was from the link above and used ObjectContext).
My context class
using System.Data.Entity;
using System.Data.Objects;
using System.Web;
using Fot.Admin.Models;
namespace Context
{
public static class ContextManager
{
internal const string DB = "MY_DB_CONTEXT";
/// <summary>
/// Get an instance that lives for the life time of the request per user and automatically disposes.
/// </summary>
/// <returns>Model</returns>
public static T AsSingleton<T>() where T : DbContext, new()
{
HttpContext.Current.Items[DB] = (T)HttpContext.Current.Items[DB] ?? new T();
return (T)HttpContext.Current.Items[DB];
}
}
}
My Context Module
using System;
using System.Data.Entity;
using System.Data.Objects;
using System.Web;
namespace Context
{
/// <summary>
/// Entity Module used to control an Entities DB Context over the lifetime of a request per user.
/// </summary>
public class ContextModule : IHttpModule
{
private const string DB = ContextManager.DB;
void context_EndRequest(object sender, EventArgs e)
{
Dispose();
}
#region IHttpModule Members
public void Dispose()
{
if(HttpContext.Current != null)
{
if (HttpContext.Current.Items[DB] != null)
{
var entitiesContext = (DbContext) HttpContext.Current.Items[DB];
entitiesContext.Dispose();
HttpContext.Current.Items.Remove(DB);
}
}
}
public void Init(HttpApplication context)
{
context.EndRequest += new EventHandler(context_EndRequest);
}
#endregion
}
}
In my web.config under <httpModules> i add this below.
<add name="ContextModule" type="Context.ContextModule" />
This ensures that the end_Request is called after every request so you can dispose the context properly.
When you need the DbContext usage is as below.
var Context = ContextManager.AsSingleton<MyDBContext>();