WebApiApplication.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dependencies;
using System.Web.Http.ExceptionHandling;
using System.Web.Http.Filters;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using DependencyInjection.AspNet.WebApi;
using IDependencyResolver = System.Web.Http.Dependencies.IDependencyResolver;
using IExceptionFilter = System.Web.Http.Filters.IExceptionFilter;

namespace YourNamespace
{
	

	/// <summary>
	/// https://stackoverflow.com/questions/50358349/using-microsoft-extension-dependencyinjection-in-asp-net-web-api2
	/// </summary>

	public class WebApiApplication : System.Web.HttpApplication
	{
		protected void Application_Start()
		{
			AreaRegistration.RegisterAllAreas();
			GlobalConfiguration.Configure(WebApiConfig.Register);
			FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
			RouteConfig.RegisterRoutes(RouteTable.Routes);
			BundleConfig.RegisterBundles(BundleTable.Bundles);

			GlobalConfiguration.Configuration.AddMicrosoftDependencyInjectionProvider(services =>
			{
				services.AddControllersAsServices(System.Reflection.Assembly.GetExecutingAssembly());
			});


		}

}