private void AddNewGadget()
        {
            Gadget           gadget           = new Gadget();
            EditGadgetWindow EditGadgetWindow = new EditGadgetWindow(gadget);

            if (EditGadgetWindow.ShowDialog() == true)
            {
                if (AppViewModel.AddGadget(gadget))
                {
                    PullAllGadgets();
                }
                else
                {
                    throw new Exception("Add Gadget Failed!");
                }
            }
        }
        private void ChangeGadget(Gadget gadget)
        {
            if (gadget == null)
            {
                MessageBox.Show("Wählen Sie bitte ein Gadget in der Liste aus");
                return;
            }
            Gadget editableGadget = new Gadget
            {
                InventoryNumber = gadget.InventoryNumber,
                Name            = gadget.Name,
                Price           = gadget.Price,
                Condition       = gadget.Condition,
                Manufacturer    = gadget.Manufacturer
            };

            EditGadgetWindow EditGadgetWindow = new EditGadgetWindow(editableGadget);

            if (EditGadgetWindow.ShowDialog() == true)
            {
                gadget.InventoryNumber = editableGadget.InventoryNumber;
                gadget.Name            = editableGadget.Name;
                gadget.Price           = editableGadget.Price;
                gadget.Condition       = editableGadget.Condition;
                gadget.Manufacturer    = editableGadget.Manufacturer;

                if (AppViewModel.UpdateGadget(gadget))
                {
                    PullAllGadgets();
                }
                else
                {
                    throw new Exception("Update Gadget Failed!");
                }
            }
        }