private async void BtnAddItem_Click(object sender, RoutedEventArgs e) { MessageDialog md; if (cvm.Categories.Count != 0) { var name = Naam.Text; var amount = 1; var categoryName = ""; try { amount = Convert.ToInt32(Amount.Text); } catch (FormatException) { md = new MessageDialog("Enter a valid number"); await md.ShowAsync(); } if (cmbCategory.SelectedItem != null) { categoryName = cmbCategory.SelectedItem.ToString(); } else { md = new MessageDialog("You have to select a category!"); } if (Naam.Text.Length != 0) { if (Amount.Text.Length != 0) { if (amount > 0) { if (cmbCategory.SelectedItem != null) { await cvm.AddNewItem(name, amount, categoryName); Naam.Text = ""; Amount.Text = ""; LvCat.ItemsSource = null; LvCat.ItemsSource = cvm.Categories; progressbar.Maximum++; var percentageDone = progressbar.Value / progressbar.Maximum * 100; ItemsDone.Text = Math.Round(percentageDone).ToString() + "%"; } else { md = new MessageDialog("Please select a category."); await md.ShowAsync(); } } else { md = new MessageDialog("Amount can't be less than or equal to 0!"); await md.ShowAsync(); } } else { md = new MessageDialog("Amount can't be empty!"); await md.ShowAsync(); } } else { md = new MessageDialog("Name can't be empty!"); await md.ShowAsync(); } } else { md = new MessageDialog("You can't add an item without a category!"); await md.ShowAsync(); } }