C# How to set proxy for all https requstest

Is it possible to add to the entire application written in C # used a proxy. Mainly because of the class I pasted below. But I also use several times the usual WebRequest.

I would like the program to use the proxy for each connection that will perform. Is it possible?

using System;
using System.Diagnostics;
using System.Net;

namespace TestV.1.0
{




    // To jest stworzenie klasy HttpHandler, dzieki której możemy pracować na http. Dziedziczy ona z klasy WebClient
    internal class HttpHandler : WebClient
    {
        //Tworzenie obiektu który będzie przechochowywał cookiesy
        public CookieContainer _container = new CookieContainer();

        protected override WebRequest GetWebRequest(Uri address)
        {
            var request = base.GetWebRequest(address);

            if (request is HttpWebRequest)
            {
                (request as HttpWebRequest).CookieContainer = _container;
            }
            return request;
        }

        protected override WebResponse GetWebResponse(WebRequest request)
        {
            var response = base.GetWebResponse(request);
            if (response != null)
            {
                var uriBuilder = new UriBuilder(response.ResponseUri.Scheme, response.ResponseUri.Host);
                _container.SetCookies(uriBuilder.Uri, _container.GetCookieHeader(request.RequestUri));
            }
            return response;
        }

        public void ClearCookies()
        {
            _container = new CookieContainer();
        }
    }

}