} //done

        static void EmployerErea(Employer_Manager _Employer)
        {
            bool   Program = true;
            string Input;

            while (Program)
            {
                Console.WriteLine("________WELCOME TO THE EMPLOYER AREA________");
                Console.WriteLine("1_Show all employers");
                Console.WriteLine("2_Add an employer");
                Console.WriteLine("3_Delete an employer");
                Console.Write("Your Choice : ");
                Input = Console.ReadLine();
                switch (Input)
                {
                case "1":
                    _Employer.ShowAll();
                    Console.WriteLine();
                    break;

                case "2":
                    Console.WriteLine();
                    string FullName;
                    int    Age;
                    Console.Write("Write the full name of the employer : ");
                    FullName = Console.ReadLine();
                    Console.Write($"Write the age of {FullName} : ");
                    try
                    {
                        Age = int.Parse(Console.ReadLine());
                        Employer E = new Employer(FullName, Age, null);
                        _Employer.Add(E);
                    }
                    catch (Exception)
                    {
                        Console.WriteLine("Age must be a number");
                    }
                    break;

                case "3":
                    Console.Write("Write the full name of the employer that you want to delete : ");
                    FullName = Console.ReadLine();
                    Employer a2 = _Employer.FindEmployer(FullName);
                    if (a2 == null)
                    {
                        Console.WriteLine("=> The command cannot be found !!");
                    }
                    else
                    {
                        _Employer.Remove(a2);
                        Console.WriteLine("->L'employer are deleted from the system.");
                    }
                    Console.WriteLine();
                    break;

                default:
                    Console.WriteLine("=> The command cannot be found !!");
                    break;
                }
                Console.WriteLine("________WELCOME TO THE EMPLOYER AREA________");
                Program = Leave();
            }
        } //done
        } //done

        static void Company(Employer_Manager _Employer, Company_Manager _Company, Company Company)
        {
            string   Input, Post;
            bool     Program = true;
            Employer a;

            while (Program)
            {
                Console.WriteLine();
                Console.WriteLine($"______WELCOME IN {Company.Name.ToUpper()}______");
                Console.WriteLine("1_Show all the employers of the company");
                Console.WriteLine("2_Show all the employer of the system");
                Console.WriteLine("3_Add an employer (from the system)");
                Console.WriteLine("4_Delete an employer");
                Console.WriteLine("5_Change the post of an employer");
                Console.WriteLine("6_Changer the salairy of an employer");
                Console.WriteLine("7_Show all posts of the company");
                Console.WriteLine("8_Add a post to the company");
                Console.WriteLine("9_Delete a post from the company");
                Console.Write("Your Choice : ");
                Input = Console.ReadLine();
                switch (Input)
                {
                case "1":
                    Console.WriteLine();
                    _Company.ShowAllEmployers(Company);
                    break;

                case "2":
                    Console.WriteLine();
                    _Employer.ShowAll();
                    break;

                case "3":
                    Console.WriteLine();
                    string FulllName;
                    Console.Write("Write the name of the employer that you want to add : ");
                    FulllName = Console.ReadLine();
                    a         = _Employer.FindEmployer(FulllName);
                    if (a == null)
                    {
                        Console.WriteLine("->The employer cannot be found.");
                    }
                    else
                    {
                        _Company.AddEmployer(Company, a);
                        Console.WriteLine($"->{a.FullName} are added to {Company.Name}");
                    }
                    break;

                case "4":
                    Console.Write("Write the name of the employer that you want to delete : ");
                    FulllName = Console.ReadLine();
                    a         = _Employer.FindEmployer(FulllName);
                    if (a == null)
                    {
                        Console.WriteLine("->The employer cannot be found.");
                    }
                    else
                    {
                        _Company.RemoveEmployer(Company, a);

                        Console.WriteLine($"->{a.FullName} are deleted from {Company.Name}");
                    }
                    Console.WriteLine();
                    break;

                case "5":
                    Console.WriteLine();
                    Console.Write("Write the name of the employer that you want to change his post  : ");
                    FulllName = Console.ReadLine();
                    a         = _Company.FindEmployerInACompany(Company, FulllName);
                    if (a == null)
                    {
                        Console.WriteLine("->The employer cannot be found.");
                    }
                    else
                    {
                        _Company.ShowAllPosts(Company);
                        Console.Write("Write the name of the post : ");
                        Post = Console.ReadLine();
                        _Company.ChangePostOfEmployer(Company, a, Post);
                    }
                    break;

                case "6":
                    Console.WriteLine();
                    Console.Write("Write the name of the employer that you want to change his salary : ");
                    FulllName = Console.ReadLine();
                    a         = _Company.FindEmployerInACompany(Company, FulllName);
                    if (a == null)
                    {
                        Console.WriteLine("->The employer cannot be found.");
                    }
                    else
                    {
                        Console.Write("Write the new salary : ");
                        int salaire = int.Parse(Console.ReadLine());
                        _Company.ChangeSalaryOfEmployer(a, salaire);
                    }
                    break;

                case "7":
                    Console.WriteLine();
                    _Company.ShowAllPosts(Company);
                    break;

                case "8":
                    Console.WriteLine();
                    Console.Write("Write the name of the new post : ");
                    Post = Console.ReadLine();
                    _Company.AddPost(Company, Post);
                    break;

                case "9":
                    Console.WriteLine();
                    _Company.ShowAllPosts(Company);
                    Console.Write("Write the name of the post that you want to delete : ");
                    Post = Console.ReadLine();
                    _Company.RemovePost(Company, Post);
                    Console.WriteLine();
                    break;

                default:
                    Console.WriteLine("=> The command cannot be found !!");
                    break;
                }
                Console.WriteLine($"______WELCOME IN {Company.Name.ToUpper()}______");
                Program = Leave();
            }
        } //done