MefDependencyResolver.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.Composition.Hosting;
using System.Linq;
using System.Web;
using System.Web.Http.Dependencies;

namespace Shop.WebApi
{
    public class MefDependencyResolver : IDependencyResolver
    {
        private CompositionContainer container;

        /// <summary>
        /// Initializes a new instance of the <see cref="MefDependencyResolver"/> class.
        /// </summary>
        /// <param name="container">MEF composition container used for DI</param>
        public MefDependencyResolver(CompositionContainer container)
        {
            this.container = container;
        }

        /// <summary>
        /// Finalizer for <see cref="MefDependencyResolver"/>
        /// </summary>
        ~MefDependencyResolver()
        {
            this.Dispose(false);
        }

        /// <inheritdoc />
        public IDependencyScope BeginScope()
        {
            return new MefDependencyResolver(new CompositionContainer(this.container.Catalog, this.container));
        }

        /// <inheritdoc />
        public void Dispose()
        {
            this.Dispose(true);
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        /// <param name="disposing">Value indicating whether this method was explicitly called</param>
        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                this.container.Dispose();
                GC.SuppressFinalize(this);
            }
        }

        /// <inheritdoc />
        public object GetService(Type serviceType)
        {
            var exports = this.container.GetExports(serviceType, null, null).FirstOrDefault();
            return exports?.Value;
        }

        /// <inheritdoc />
        public IEnumerable<object> GetServices(Type serviceType)
        {
            var exports = this.container.GetExports(serviceType, null, null);
            var result = new List<object>(exports.Count());
            foreach (var export in exports)
            {
                result.Add(export.Value);
            }

            return result;
        }
    }
}