using System;

using Ardalis.GuardClauses;

public class Program

{

    public static void Main()

    {

        var employee = new Employee("Joe", "Smith", DateTime.Now, 10);

        Console.WriteLine(employee.DateOfBirth);

    }

}

​

public class Employee

{

    public int Id { get; set; }

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public decimal Salary { get; set; }

    public DateTime DateOfBirth { get; set; }

    #pragma warning disable CS8618 // Required by Entity Framework

    private Employee() {}

    public Employee(string firstName, string lastName, DateTime dateOfBirth, decimal salary)

    {

        FirstName = Guard.Against.NullOrWhiteSpace(nameof(firstName), firstName);

        LastName = Guard.Against.NullOrWhiteSpace(nameof(lastName), lastName);

        Salary = Guard.Against.NegativeOrZero(salary, nameof(salary));

        DateOfBirth = Guard.Against.AgainstExpression(date => date.Date > DateTime.Now.Date , dateOfBirth, "test");

    }

}