UnityPerRequestHttpModule.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Unity.Lifetime;

namespace Unity.AspNet.WebApi
{
    public class UnityPerRequestHttpModule : IHttpModule
    {
        private static readonly object ModuleKey = new object();

        internal static object GetValue(object lifetimeManagerKey)
        {
            var dict = GetDictionary(HttpContext.Current);

            if (dict != null)
            {
                if (dict.TryGetValue(lifetimeManagerKey, out var obj))
                {
                    return obj;
                }
            }

            return LifetimeManager.NoValue;
        }

        internal static void SetValue(object lifetimeManagerKey, object value)
        {
            var dict = GetDictionary(HttpContext.Current);

            if (dict == null)
            {
                dict = new Dictionary<object, object>();

                HttpContext.Current.Items[ModuleKey] = dict;
            }

            dict[lifetimeManagerKey] = value;
        }

        /// <summary>
        /// Disposes the resources used by this module.
        /// </summary>
        public void Dispose()
        {
        }

        /// <summary>
        /// Initializes a module and prepares it to handle requests.
        /// </summary>
        /// <param name="context">An <see cref="HttpApplication"/> that provides access to the methods, properties,
        /// and events common to all application objects within an ASP.NET application.</param>
        public void Init(HttpApplication context)
        {
            (context ?? throw new ArgumentNullException(nameof(context))).EndRequest += OnEndRequest;
        }

        private void OnEndRequest(object sender, EventArgs e)
        {
            var app = (HttpApplication)sender;

            var dict = GetDictionary(app.Context);

            if (dict != null)
            {
                foreach (var disposable in dict.Values.OfType<IDisposable>())
                {
                    disposable.Dispose();
                }
            }
        }

        private static Dictionary<object, object> GetDictionary(HttpContext context)
        {
            if (context == null)
            {
                throw new InvalidOperationException(
                    "The PerRequestLifetimeManager can only be used in the context of an HTTP request.Possible causes for this error are using the lifetime manager on a non-ASP.NET application, or using it in a thread that is not associated with the appropriate synchronization context.");
            }

            var dict = (Dictionary<object, object>)context.Items[ModuleKey];

            return dict;
        }
    }
}