Fluent builder example

FluentBuilderExample.cs

var person = PersonBuilder.Create()
    .Age(30)
    .FirstName("First")
    .LastName("Last")
    .Build();

Console.WriteLine(person);

public interface IPersonBuilder
{
    Person Build();
    IPersonBuilder FirstName(string value);
    IPersonBuilder LastName(string value);
    IPersonBuilder Age(int age);
}

public sealed class PersonBuilder : IPersonBuilder
{
    private Person _person;

    public PersonBuilder()
    {
        _person = new Person();
    }

    public static IPersonBuilder Create() => new PersonBuilder();

    public Person Build() => _person;

    public IPersonBuilder FirstName(string value)
    {
        _person.FirstName = value;
        return this;
    }

    public IPersonBuilder LastName(string value)
    {
        _person.LastName = value;
        return this;
    }

    public IPersonBuilder Age(int age)
    {
        _person.Age = age;
        return this;
    }
}

public record Person
{
    public string FirstName { get; set; } = "";
    public string LastName { get; set; } = "";
    public int? Age { get; set; }

    public override string ToString()
    {
        return $"{LastName}, {FirstName} {Age}";
    }
}