private void btnEditEmployee_Click(object sender, RoutedEventArgs e)
 {
     if (EmployeesGrid.SelectedIndex >= 0)
     {
         currentEmployee = EmployeesGrid.SelectedItem as Employee;
         AddEditEmployee addWindow = new AddEditEmployee(employeeDataAccess, currentEmployee);
         addWindow.ShowDialog();
     }
 }
        private void btnAddEmployee_Click(object sender, RoutedEventArgs e)
        {
            AddEditEmployee addWindow = new AddEditEmployee(employeeDataAccess);

            addWindow.ShowDialog();
        }