public MainWindow()
{
InitializeComponent();
_vm = new ClientViewModel();
this.DataContext = _vm;
_vm.LoadClients();
_vl = new MaterielViewModel();
this.DataContext = _vl;
_vl.LoadMateriels();
_vn = new SiteViewModel();
this.DataContext = _vn;
_vn.LoadSites();
_vp = new InterventionViewModel();
this.DataContext = _vp;
_vp.LoadInterventions();
WindowStartupLocation = System.Windows.WindowStartupLocation.CenterScreen;
}