Check null field with ?? - CSharp Language Basics

CSharp examples for Language Basics:Nullable

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Description

Check null field with ??

Demo Code

using System;/*from ww  w  .  j ava  2 s.c o m*/
using System.Collections.Generic;
using System.Text;
public class FastRunner : Runnable
{
   public void Run(int distance)
   {
      Console.WriteLine($"Running fast for {distance} kms");
   }
}
public interface Runnable
{
   void Run(int distance);
}
public class Person
{
   public string FirstName { get; private set; }
   public string LastName { get; private set; }
   private Runnable _runner;
   public Person(string firstName, string lastName, Runnable runner)
   {
      FirstName = firstName;
      LastName = lastName;
      _runner = runner ?? throw new ArgumentNullException("runner");
   }
   public void Run(int distance)
   {
      _runner.Run(distance);
   }
}
class Program
{
   static void Main(string[] args)
   {
      try
      {
         Person p = new Person("John", "Smith", new SlowRunner());
         p.Run(9);
      }
      catch(ArgumentNullException e)
      {
         Console.WriteLine("Runner cannot be null");
      }
      catch(Exception e)
      {
         Console.WriteLine("Oops something went wrong");
      }
   }
}
public class SlowRunner : Runnable
{
   public void Run(int distance)
   {
      Console.WriteLine($"Running slow for {distance} kms");
   }
}

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