C# - Implementing a Custom Equality Comparer

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Create a list of Person objects
        var people = new List<Person>
        {
            new Person { Id = 1, Name = "John" },
            new Person { Id = 2, Name = "Alice" },
            new Person { Id = 3, Name = "Bob" }
        };

        // Create a custom equality comparer based on the Id property
        var idEqualityComparer = new IdEqualityComparer();

        // Use the custom equality comparer to find a person by Id
        var personToFind = new Person { Id = 2, Name = "Unknown" };
        var foundPerson = people.Find(p => idEqualityComparer.Equals(p, personToFind));

        if (foundPerson != null)
        {
            Console.WriteLine($"Found person: {foundPerson.Name}");
        }
        else
        {
            Console.WriteLine("Person not found.");
        }
    }
}

class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

class IdEqualityComparer : IEqualityComparer<Person>
{
    public bool Equals(Person x, Person y)
    {
        if (ReferenceEquals(x, y)) return true;
        if (x is null || y is null) return false;
        return x.Id == y.Id;
    }

    public int GetHashCode(Person obj)
    {
        if (obj is null) return 0;
        return obj.Id.GetHashCode();
    }
}