#355 – Implementing Three-State CheckBox Dependent Behavior

You can use a three-state CheckBox to reflect the state of a set of other CheckBox controls.

Here’s some sample code that implements this behavior.  (See the previous post for the XAML).

    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        private bool doEat;
        public bool DoEat
        {
            get { return doEat; }
            set
            {
                doEat = value;
                OnPropertyChanged("DoEat");
                OnPropertyChanged("DoEverything");
            }
        }

        // Add same code for DoPray and DoLove properties here

        // Nullable bool - can be true, false or null
        public bool? DoEverything
        {
            get
            {
                if (DoEat && DoPray && DoLove)
                    return true;
                else if (!DoEat && !DoPray && !DoLove)
                    return false;
                else
                    return null;
            }

            set
            {
                if (value == true)
                    DoEat = DoPray = DoLove = true;
                else
                    DoEat = DoPray = DoLove = false;
            }
        }

        public MainWindow()
        {
            this.InitializeComponent();
            this.DataContext = this;
        }

        private void OnPropertyChanged(string prop)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }
    }
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