. Dependency injection of NETCORE

//MVC Three built-in dependency injection methods

        //MVC Three built-in dependency injection methods 
        public WeatherForecastController(ILogger<WeatherForecastController> logger, IConfiguration configuration, IHostEnvironment hostEnvironment)
        {
    
            _logger = logger;
            this.configuration = configuration;
            this.hostEnvironment = hostEnvironment;
        }

        [HttpGet]
        public IEnumerable<WeatherForecast> Get()
        {
    
            var rng = new Random();
            // The second dependency injection method 
            IHostEnvironment host = HttpContext.RequestServices.GetService(typeof(IHostEnvironment)) as IHostEnvironment;
            // The third way of dependency injection 
            var host2 = HttpContext.RequestServices.GetRequiredService<IHostEnvironment>();
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
    
                Date = DateTime.Now.AddDays(index),
                TemperatureC = rng.Next(-20, 55),
                Summary = Summaries[rng.Next(Summaries.Length)]
            })
            .ToArray();
        }

        public void ConfigureServices(IServiceCollection services)
        {
    
            services.AddControllers();
            services.AddSingleton<IServiceCollection>();// It's the same one every time 
            services.AddScoped<ILogger>(); // This time into Controller Of URL  Get the same 
            services.AddTransient<ILogger>(); // Every time it's new 

            services.AddSingleton<IServiceCollection>(x => new ServiceCollection());
            // Equate to 
            services.AddSingleton<IServiceCollection, ServiceCollection>();

        }