radCheckedDropDownList - How do I make it so the user can't type in the edit box?

        public RadForm1()
        {
            InitializeComponent();

            this.radCheckedDropDownList1.CheckedDropDownListElement.AutoCompleteEditableAreaElement.AutoCompleteTextBox.KeyPress += AutoCompleteTextBox_KeyPress;

        }

        private void AutoCompleteTextBox_KeyPress(object sender, KeyPressEventArgs e)
        {
            e.Handled = true;
        }