MefToExtendAHttpModule

example1.cs

public interface ISetCookies
{
    void SetCookie(HttpContext context);
}

example2.cs

[Import]
public IEnumerable<ISetCookies> CookieSetters { get; set; }

example3.cs

public void Init(HttpApplication context)
{
    // Setup the MEF container
    var catalog  = DirectoryCatalog(context.Request.PhysicalApplicationPath + "\\bin");
    var container = new CompositionContainer(catalog);
    var batch = new CompositionBatch();
    batch.AddPart(this);
    container.Compose(batch);

    // Setup events
    context.PostAuthenticateRequest += new EventHandler(Context_PostAuthenticateRequest);
    context.PostAuthorizeRequest += new EventHandler(Context_PostAuthorizeRequest);
}

example4.cs

void Context_PostAuthorizeRequest(object sender, EventArgs e)
{
    var context = ((HttpApplication) sender).Context;
    if (context != null)
    {
        foreach (var setter in CookieSetters)
        {
            setter.SetCookie(context);
        }
      }
}

example5.cs

namespace Keith.SimpleCookie
{
    [Export(typeof(ISetCookies))]
    public class SimpleCookie : ISetCookies
    {
        public void SetCookie(HttpContext context)
        {
            context.Response.Cookies.Add(new HttpCookie("Name", context.User.Identity.Name));
        }
    }
}