When you look at the line above ConfigureServices are you seeing the other references ?
Here is my code that works fine
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Razor;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Nop.Core.Infrastructure;
using Nop.Plugin.Apollo.Appointments.ViewEngine;
using System;
using System.Collections.Generic;
using System.Text;
namespace Nop.Plugin.Apollo.Appointments.ActionFilter
{
public class Startup : INopStartup
{
/// <summary>
/// Add and configure any of the middleware
/// </summary>
/// <param name="services">Collection of service descriptors</param>
/// <param name="configuration">Configuration of the application</param>
public void ConfigureServices(IServiceCollection services, IConfiguration configuration)
{
//add object context
services.Configure<MvcOptions>(congig => {
congig.Filters.Add<ApolloActionFilter>();
});
services.Configure<RazorViewEngineOptions>(o =>
{
o.ViewLocationExpanders.Add(new CustomViewEngine());
});
// Add framework services.
services.AddMvc();
}
/// <summary>
/// Configure the using of added middleware
/// </summary>
/// <param name="application">Builder for configuring an application's request pipeline</param>
public void Configure(IApplicationBuilder application)
{
}
public int Order
{
get { return int.MaxValue; }
}
}
}
Also no need to start a new thread
https://www.nopcommerce.com/en/boards/topic/91927/startup-class-in-a-plugin-at-nop-440-not-called-up