Runtime Dependent ListBox

using System;
using System.ComponentModel;
using System.Web;
using System.Web.UI;

namespace MagicAjax.UI.Controls
{
	#region Class KeyPressEventArgs
	public class KeyPressEventArgs : EventArgs
	{
		private char _keyChar;

		public char KeyChar
		{
			get { return _keyChar; }
		}

		public KeyPressEventArgs (char keyChar)
		{
			this._keyChar = keyChar;
		}
	}
	#endregion

	#region Class KeyEventArgs
	public class KeyEventArgs : EventArgs
	{
		private int _keyCode;
		private bool _alt, _control, _shift;

		public int KeyCode
		{
			get { return _keyCode; }
		}

		public bool Alt
		{
			get { return _alt; }
		}

		public bool Control
		{
			get { return _control; }
		}

		public bool Shift
		{
			get { return _shift; }
		}

		public KeyEventArgs (int keyCode, bool alt, bool control, bool shift)
		{
			this._keyCode = keyCode;
			this._alt = alt;
			this._control = control;
			this._shift = shift;
		}
	}
	#endregion

	public delegate void KeyPressEventHandler (object sender, KeyPressEventArgs e);
	public delegate void KeyEventHandler (object sender, KeyEventArgs e);

	/// <summary>
	/// Captures the KeyPress, KeyDown, and KeyUp client events of its inner controls.
	/// </summary>
	/// <remarks>
	/// The KeyPress event has the IE behaviour across all browsers (invoked when a character
	/// is typed or Enter is pressed).
	/// </remarks>
	[ToolboxData("<{0}:KeyClientEventWrapper runat=server>Insert controls to capture their OnKey events</{0}:KeyClientEventWrapper>")]
	public class KeyClientEventWrapper : BaseClientEventWrapper
	{
		public event KeyPressEventHandler KeyPress;
		public event KeyEventHandler KeyDown;
		public event KeyEventHandler KeyUp;

		protected override void HandleEvent(string eventName, string argument)
		{
			switch (eventName)
			{
				case "keypress" :
					OnKeyPress (new KeyPressEventArgs((char)Int32.Parse(argument)));
					break;

				case "keydown" :
					OnKeyDown (CreateKeyEventArgs(argument));
					break;

				case "keyup" :
					OnKeyUp (CreateKeyEventArgs(argument));
					break;

				default:
					throw new MagicAjaxException(String.Format("Invalid event name '{0}' captured by {1}.", eventName, ClientID));
			}
		}

		protected override void AttachClientEvents(HtmlTextWriter writer)
		{
			if ( KeyPress != null )
				writer.AddAttribute ("onkeypress", String.Format("__onKeyPress(event,'{0}');", UniqueID));

			if ( KeyDown != null )
				writer.AddAttribute ("onkeydown", String.Format("__onKeyUpDown(event,'keydown','{0}');", UniqueID));

			if ( KeyUp != null )
				writer.AddAttribute ("onkeyup", String.Format("__onKeyUpDown(event,'keyup','{0}');", UniqueID));
		}

		protected override void OnPreRender(EventArgs e)
		{
			string onKeyScript = @"<script type='text/javascript'>
				<!--
				function __onKeyPress(e,src)
				{
					if ('which' in e && e.keyCode!=13)
					{
						if (e.which>=32)
							__doPostBack(src,'keypress;'+e.which);
					}
					else
					{
						__doPostBack(src,'keypress;'+e.keyCode);
					}
				}
				function __onKeyUpDown(e,evtname,src)
				{
					__doPostBack(src,evtname+';'+e.keyCode+','+e.altKey+','+e.ctrlKey+','+e.shiftKey);
				}
				// -->
				</script>";

			base.OnPreRender (e);
			if ( ! Page.IsClientScriptBlockRegistered("__ONKEYBLOCK") )
				Page.RegisterClientScriptBlock("__ONKEYBLOCK", onKeyScript);
		}

		protected virtual KeyEventArgs CreateKeyEventArgs (string argument)
		{
			int keyCode;
			bool alt, control, shift;

			try
			{
				string[] args = argument.Split(',');
                keyCode = Int32.Parse(args[0]);
				alt = Boolean.Parse(args[1]);
				control = Boolean.Parse(args[2]);
				shift = Boolean.Parse(args[3]);

				return new KeyEventArgs(keyCode, alt, control, shift);
			}
			catch
			{
				throw new MagicAjaxException(String.Format("Invalide KeyEvent argument '{0}' for {1}.", argument, ClientID));
			}
		}

		protected virtual void OnKeyPress (KeyPressEventArgs e)
		{
			if (KeyPress != null)
				KeyPress (this, e);
		}

		protected virtual void OnKeyDown (KeyEventArgs e)
		{
			if (KeyDown != null)
				KeyDown (this, e);
		}

		protected virtual void OnKeyUp (KeyEventArgs e)
		{
			if (KeyUp != null)
				KeyUp (this, e);
		}
	}
}