If both text boxes contain a number, there is no need to convert to integer because it has assigned itself as an int (or so it should be). You are also assigning it to an int variable.Code:private void button_Click(object sender, RoutedEventArgs e) { int aantaltextBox = textBox.Text; int limiet = textBox1.Text; int aantallabel = label.Content=0; while (aantallabel < limiet) { label.Content = aantallabel + aantaltextBox; }