private static void InsertNewEmployee(SoftUniEntities db, string firstName, string lastName, string middleName,
            string jobTitle, string department, string manager, DateTime dateTime, double salary, string address)
        {
            var idDepartment = db.Departments.FirstOrDefault(d => d.Name == department).DepartmentID;
            var idManager = db.Employees.FirstOrDefault(e => e.FirstName + " " + e.LastName == manager).EmployeeID;
            var idAddress = db.Addresses.FirstOrDefault(a => a.AddressText == address).AddressID;

            var newEmployee = new Employee
            {
                FirstName = firstName,
                LastName = lastName,
                MiddleName = middleName,
                AddressID = idAddress,
                ManagerID = idManager,
                DepartmentID = idDepartment,
                JobTitle = jobTitle,
                HireDate = dateTime,
                Salary = (decimal)salary
            };

            db.Employees.Add(newEmployee);
            db.SaveChanges();
        }
        private static void ModifyEmployee(SoftUniEntities db, int id, string firstName, string lastName,
            string middleName, string jobTitle, string department, string manager, DateTime dateTime, double salary,
            string address)
        {
            var employee = db.Employees.FirstOrDefault(e => e.EmployeeID == id);
            if (employee == null)
            {
                throw new NullReferenceException();
            }
            employee.DepartmentID = db.Departments.FirstOrDefault(d => d.Name == department).DepartmentID;
            employee.ManagerID = db.Employees.FirstOrDefault(e => e.FirstName + " " + e.LastName == manager).EmployeeID;
            employee.AddressID = db.Addresses.FirstOrDefault(a => a.AddressText == address).AddressID;
            employee.FirstName = firstName;
            employee.LastName = lastName;
            employee.MiddleName = middleName;
            employee.Salary = (decimal)salary;
            employee.HireDate = dateTime;
            employee.JobTitle = jobTitle;

            db.Entry(db.Employees.FirstOrDefault(e => e.EmployeeID == id)).CurrentValues.SetValues(employee);
            db.SaveChanges();
        }
 private static void DeleteEmployee(SoftUniEntities db, int id)
 {
     var employee = db.Employees.FirstOrDefault(e => e.EmployeeID == id);
     db.Employees.Remove(employee);
     db.SaveChanges();
 }