When You proper the ItemsSource with the correct price XAML does not automatically reilitialize the collection of things. So your DataContext for "video_length_textbox" is about to itself, along with your IncrementingTextBox course does not have a general public property known as ConfigurationModel OldCurmudgeonOldCurmudgeon 66k1818 gold badges126126 silver badges220220 bronze badges https://www.tumblr.com/m3mprojectsingurgaon