public void ConfigureServices(IServiceCollection services)
{
   services.AddMySampleLib(new SmtpConfig { /*...*/ });

using System.IO;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Html;

namespace Sample
{
    /// <summary>
    /// Html Helper Extensions
    /// </summary>
    public static class HtmlHelperExtensions
    {
        /// <summary>
        /// Convert IHtmlContent/TagBuilder to string
        /// </summary>
        public static string GetString(this IHtmlContent content)
        {
            using (var writer = new StringWriter())
            {
                content.WriteTo(writer, HtmlEncoder.Default);
                return writer.ToString();
            }
        }
    }
}

  <system.webServer>
    <modules runAllManagedModulesForAllRequests="true" >

 routes.MapRoute(
                name: "joomla",
                url: "fa/index.php",
                defaults: new { controller = "Joomla", action = "Index" }
            );

using System.Web.Mvc;

namespace MVC5Basic.Controllers
{
    public class JoomlaController : Controller
    {
        public ActionResult Index(string option, string view, string id, string itemid)
        {
            //todo: process parameters and then return something!
            return View();
        }
    }
}

public class CustomValidationAttribute : ValidationAttribute   
{ 
    protected override ValidationResult IsValid(object value, ValidationContext validationContext) 
    { 
        var service = validationContext.GetService(typeof(IExternalService)); 
        // use service 
    } 
}