TriStateRadio User Control with DataBinding

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;

namespace TriStateRadioControlLibrary
{
    [System.ComponentModel.DefaultBindingProperty("Checked")] //simple binding attribute
    public partial class TriStateRadio : UserControl, INotifyPropertyChanged
    {
        // properties for external access
        public String TextTrueRadio { get { return radioButton1.Text; } set { radioButton1.Text = value; } }
        public String TextFalseRadio { get { return radioButton2.Text; } set { radioButton2.Text = value; } }
        public String TextNullRadio { get { return radioButton3.Text; } set { radioButton3.Text = value; } }

        public Nullable<bool> _checked;
        // binding property
        public Nullable<bool> Checked
        {
            get { return _checked; }
            set
            {
                if (value != _checked)
                {
                    _checked = value;
                    OnPropertyChanged("Checked");
                }
            }
        }

        private void CheckChanged() //update bool field
        {
            switch (_checked)
            {
                case true:
                    radioButton1.Checked = true;
                    break;
                case false:
                    radioButton2.Checked = true;
                    break;
                case null:
                    radioButton3.Checked = true;
                    break;
                default:
                    throw new Exception("Error selecting TriStateRadio state!");
                    //break;
            }
        }



        public TriStateRadio()
        {
            InitializeComponent();
        }

        //events for changing between radio buttons
        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {
            if (this.radioButton1.Checked == true)
            {
                this.Checked = true;
            }
        }

        private void radioButton2_CheckedChanged(object sender, EventArgs e)
        {
            if (this.radioButton2.Checked == true)
            {
                this.Checked = false;
            }
        }

        private void radioButton3_CheckedChanged(object sender, EventArgs e)
        {
            if (this.radioButton3.Checked == true)
            {
                this.Checked = null;
            }
        }


        #region PropertyChangeNotification
        protected void OnPropertyChanged(PropertyChangedEventArgs e)
        {

            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
                handler(this, e);
        }

        public void OnPropertyChanged(string propertyName)
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
        }

        
        public event PropertyChangedEventHandler PropertyChanged;
        
        #endregion

        //necesary to update control interface when loaded
        private void TriStateRadio_Load(object sender, EventArgs e)
        {
            PropertyChanged += new PropertyChangedEventHandler(TriStateRadio_PropertyChanged);
            CheckChanged();
        }

        void TriStateRadio_PropertyChanged(object sender, EventArgs e)
        {
            CheckChanged(); //this can be used with EventArgs to detect which property has actually changed
        }

    }
}