PasswordTextBox for Silverlight 2 Beta 2

/// Copyright 2008 Chris Pietschmann ()
/// This work is licensed under a Creative Commons Attribution 3.0 United States License
/// http://creativecommons.org/licenses/by/3.0/us/
///
/// This is a Password TextBox built for use with Silverlight 2 Beta 1
/// The reason this was built, is because the standard TextBox in
/// Silverlight 2 Beta 1 does not have Password support.
/// Original Link: /post/2008/03/PasswordTextBox-for-Silverlight-2-Beta-1.aspx
/// 

using System.Windows.Controls; 

namespace SilverlightPasswordTextBox
{
    public partial class PasswordTextBox : TextBox
    {
        public PasswordTextBox()
        {
            this.TextChanged += new TextChangedEventHandler(PasswordTextBox_TextChanged);

            this.KeyDown += new System.Windows.Input.KeyEventHandler(PasswordTextBox_KeyDown);
        } 

        #region Event Handlers 

        public void PasswordTextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (base.Text.Length >= _Text.Length)
                _Text += base.Text.Substring(_Text.Length);
            DisplayMaskedCharacters();
        } 

        public void PasswordTextBox_KeyDown(object sender, System.Windows.Input.KeyEventArgs e)
        {
            int cursorPosition = this.SelectionStart;
            int selectionLength = this.SelectionLength; 

            // Handle Delete and Backspace Keys Appropriately
            if (e.Key == System.Windows.Input.Key.Back
                || e.Key == System.Windows.Input.Key.Delete)
            {
                if (cursorPosition < _Text.Length)
                    _Text = _Text.Remove(cursorPosition, (selectionLength > 0 ? selectionLength : 1));
            }

            base.Text = _Text;

            this.Select((cursorPosition > _Text.Length ? _Text.Length : cursorPosition), 0);

            DisplayMaskedCharacters();
        } 

        #endregion 

        #region Private Methods 

        private void DisplayMaskedCharacters()
        {
            int cursorPosition = this.SelectionStart;

            // This changes the Text property of the base TextBox class to display all Asterisks in the control
            base.Text = new string(_PasswordChar, _Text.Length); 

            this.Select((cursorPosition > _Text.Length ? _Text.Length : cursorPosition), 0);
        } 

        #endregion 

        #region Properties 

        private string _Text = string.Empty;

        /// <summary>
        /// The text associated with the control.
        /// </summary>
        public new string Text
        {
            get { return _Text; }
            set
            {
                _Text = value;
                DisplayMaskedCharacters();
            }
        } 

        private char _PasswordChar = &'*&';

        /// <summary>
        /// Indicates the character to display for password input.
        /// </summary>
        public char PasswordChar
        {
            get { return _PasswordChar; }
            set { _PasswordChar = value; }
        } 

        #endregion
    }
}