public MainWindow()
 {
     InitializeComponent();
     SpecialeControls();
     EnableDisableButtons(false);
     ValidatieDeelnemer(grdTop);
     beheerControls.AlleTextBoxenNormaal();
 }
 void MaakVeldenDeelnemersLeeg()
 {
     lstMailingList.SelectedIndex = -1;
     lblId.Content = "";
     txtFirstName.Clear();
     txtLastName.Clear();
     txtEmail.Clear();
     txtPhone.Clear();
     txtStreet.Clear();
     txtStreetNumber.Clear();
     txtCity.Clear();
     txtPostalCode.Clear();
     VulList();
     deelnemer_Sel = null;
     beheerControls.AlleTextBoxenNormaal();
     EnableDisableButtons(false);
 }