records.cs

using System;

static void Run()
{
    Employee foo = new Employee("Aysha", "Stein", "1234");
    Person bar = (Person)foo with { FirstName = "John", LastName = "Doe"};

    Console.WriteLine($"foo: {foo}");
    Console.WriteLine($"bar: {bar}");

    // Expected Output:

    // 1) foo: Employee { FirstName = Aysha, LastName = Stein, EmployeeNumber = 1234 }
    //    bar: Employee { FirstName = John, LastName = Doe, EmployeeNumber = 1234 }

    // 2) foo: Employee { FirstName = John, LastName = Doe, EmployeeNumber = 1234 }
    //    bar: Employee { FirstName = John, LastName = Doe, EmployeeNumber = 1234 }

    // 3) foo: Employee { FirstName = Aysha, LastName = Stein, EmployeeNumber = 1234 }
    //    bar: Person { FirstName = John, LastName = Doe }

    // 4) foo: Employee { FirstName = John, LastName = Doe, EmployeeNumber = 1234 }
    //    bar: Person { FirstName = John, LastName = Doe }
}

Run();

public record Person(string FirstName, string LastName);
public record Employee(string FirstName, string LastName, string EmployeeNumber) : Person(FirstName, LastName);