Service.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BehavioralPatterns.NullObject
{
 class Service
 {
 private ILog log;

 public Service(ILog log)
 {
 this.log = log;
 }

 public void HandleRequestWithoutNullObject(string request)
 {
 if (log != null)
 {
 log.Write(request);
 }

 // more statements

 if (log != null)
 {
 log.Write(request);
 }
 }

 public void HandleRequestWithNullObject(string request)
 {
 log.Write(request);
 }

 public void HandleRequestWithNullPropagation(string request)
 {
 log?.Write(request);
 }
 }
}