public class Person
{
     public string Firstname { get; private set; }
     public string Lastname { get; private set; }

     private Person(string firstname, string lastname)
     {
          ArgumentNullException.ThrowIfNull(firstname);
          ArgumentNullException.ThrowIfNull(lastname);
          Firstname = firstname;
          Lastname = lastname;
     }
     
     public static Person Create(string firstname, string lastname)
     {
          return new Person(firstname, lastname);
     }
}

public void CreateNewPerson()
{
     Person.Create("AmirAbbas", "Mottaghipour");
}

using Nilgon.Condition.Helpers;

public Person(string firstname)
{
     if (firstname.IsNull() && firstname.IsEmpty())
     {
          throw ...;
     }
}

public Person(string firstname, string lastname)
{
     Firstname = firsname.MustNotBeNull();
     Lastname = lastname.MustNotBeNull();
}