Databindings for custom control wont work?

I am having trouble understanding why my databindings do not seem to work with my custom class. I made (hacked) my class extend the Control class to add the databindings functionality but it doesn't actually bind to my custom property.

My code for my custom class is:

    public class RadioButtonSet : System.Windows.Forms.Control
    {

        private Dictionary<System.Windows.Forms.RadioButton, int> buttonList;
        private int selectedValue;

        public RadioButtonSet()
        {
            buttonList = new Dictionary<System.Windows.Forms.RadioButton, int>();
        }

        public void AddButton(System.Windows.Forms.RadioButton button, int buttonValue)
        {
            if (this.buttonList.ContainsKey(button))
                throw new Exception("Button set already contains specified button");
            else if (buttonValue <= 0)
                throw new Exception("Cannot add specified key to button set");
            else if (button == null)
                throw new Exception("Parameter button cannot be null");
            else
            {
                button.CheckedChanged += button_CheckedChanged;
                this.buttonList.Add(button, buttonValue);
            }
        }

        private void setSelectedButton()
        {
            this.buttonList.FirstOrDefault(x => x.Value == this.selectedValue).Key.Checked = true;
        }

        private void button_CheckedChanged(object sender, EventArgs e)
        {
            System.Windows.Forms.RadioButton btn = sender as System.Windows.Forms.RadioButton;
            this.selectedValue = this.buttonList[btn];
        }

        public int SelectedButton
        {
            get
            {
                return selectedValue;
            }
            set
            {
                selectedValue = value;
                setSelectedButton();
            }
        }

    }

And I try to bind to this class using the following, where rbs_admin is an instance of my custom class:

rbs_admin.DataBindings.Add("SelectedButton", datatable, "admin");

I do not know what information may help so here goes.

I get the information to bind from a datatable which is populated by a data adapter. This custom class is not in it's own file, its part of another static class in my project.

I just dont understand as I created a custom textbox with the same custom property and it binds and works fine.

Any help is much appreciated.