#854 – Clicked vs. Checked/Unchecked Events for CheckBox

If you want to add an event handler for a CheckBox that gets executed whenever a user clicks on the CheckBox, you can take one of two different approaches:

• Add a handler for the Click event and then check the IsChecked property to discover the new state (checked / unchecked / indeterminate)
• Handle one or more of the specific events for the individual states–Checked, Unchecked or Indeterminate

When a user clicks on the CheckBox, the specific event (e.g. Checked) is fired, followed by the Click event.

        private void CheckBox_Click(object sender, RoutedEventArgs e)
        {
            CheckBox cb = sender as CheckBox;
            string checkState;

            if (!cb.IsChecked.HasValue)
                checkState = "Indeterminate";
            else
            {
                if (cb.IsChecked == true)
                    checkState = "Checked";
                else
                    checkState = "Unchecked";
            }

            Trace.WriteLine(string.Format("Click event: {0}", checkState));
        }

        private void CheckBox_Checked(object sender, RoutedEventArgs e)
        {
            Trace.WriteLine("Checked event");
        }

        private void CheckBox_Unchecked(object sender, RoutedEventArgs e)
        {
            Trace.WriteLine("Unchecked event");
        }

        private void CheckBox_Indeterminate(object sender, RoutedEventArgs e)
        {
            Trace.WriteLine("Indeterminate event");
        }