An improvement to RegisterClientScriptBlock

using System;
using System.Collections;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace CodeProject
{
	/// <summary>
	/// A base page class from which all web pages can be derived. The main
	/// purpose of this class is to provide more complete handling of client
	/// side javascript rendering.
	/// </summary>
	public class ScriptPage : System.Web.UI.Page
	{
		protected Hashtable	m_ClientScripts;		// Set of client side scripts to output in HTML header
		public    Literal   _clientScript;			// Placeholder for script output in the webpage

		/// <summary>
		/// Constructor
		/// </summary>
		public ScriptPage() : base()
		{
			m_ClientScripts = new Hashtable();
		}

		#region Protected methods
		/// <summary>
		/// Send a trace statement to the Trace Context
		/// </summary>
		/// <param name="str">String to output</param>
		protected void DbgTrace(string str)
		{
			if (HttpContext.Current != null && Trace != null && Trace.IsEnabled)
			{
				Trace.Write(ToString(), str);
			}
		}

		/// <summary>
		/// Gets the complete HTML describing the client-side scripts to output as part
		/// of this page's headers
		/// </summary>
		protected string ClientScript
		{
			get
			{
				StringBuilder script = new StringBuilder();

				if (m_ClientScripts != null)
					foreach (object scriptBlock in m_ClientScripts.Values)
						script.Append(scriptBlock.ToString() + "\n");

				//DbgTrace("ClientScript is " + script.ToString());

				return script.ToString();
			}
		}
		#endregion

		#region Public methods

		/// <summary>
		/// Registers a client side javascript event handler
		/// </summary>
		/// <param name="key">script key. If a script is already registered using this key then the 
		/// previous script is replaced</param>
		/// <param name="eventName">The event to handle</param>
		/// <param name="ctrlName">The name of the HTML element(s) to apply this handler to</param>
		/// <param name="script">The script to run</param>
		public virtual void RegisterClientScriptEvent(string key, string eventName, string ctrlName, string script)
		{
			RegisterClientScriptEvent(key, eventName, ctrlName, script, "Javascript");
		}

		/// <summary>
		/// Registers a client side javascript event handler
		/// </summary>
		/// <param name="key">script key. If a script is already registered using this key then the 
		/// previous script is replaced</param>
		/// <param name="eventName">The event to handle</param>
		/// <param name="ctrlName">The name of the HTML element(s) to apply this handler to</param>
		/// <param name="script">The script to run</param>
		/// <param name="language">The script's language</param>
		public virtual void RegisterClientScriptEvent(string key, string eventName, string ctrlName, string script, 
			                                          string language)
		{
			// client-side event handling only in IE 4 and above
			if (Request.Browser.Browser.ToUpper().IndexOf("IE") < 0 || 
				Double.Parse(Request.Browser.Version) < 4.0)
				return;

			StringBuilder block = new StringBuilder();
			block.Append("<script type=\"text/javascript\" language=\"");
			block.Append(language);
			block.Append("\" for=\"");
			block.Append(ctrlName);
			block.Append("\" event=\"");
			block.Append(eventName);
			block.Append("\" defer=\"true\"><!--\n");
			block.Append(script);
			block.Append("\n//--></script>");

			if (!m_ClientScripts.ContainsKey(key))
			{
				m_ClientScripts.Add(key, block);
				//DbgTrace("Adding script: " + key + " - " + block);
			}
			else
			{
				m_ClientScripts[key] = block;
				//DbgTrace("Replacing file: " + key + " - " + block);
			}
		}

		/// <summary>
		/// Registers a client side javascript file include
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="file">The javascript include file to reference</param>
		public virtual void RegisterClientScriptFile(string key, string file)
		{
			RegisterClientScriptFile(key, file, "Javascript", false);
		}

		/// <summary>
		/// Registers a client side javascript file include
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="file">The javascript include file to reference</param>
		/// <param name="language">The script's language</param>
		public virtual void RegisterClientScriptFile(string key, string file, string language)
		{
			RegisterClientScriptFile(key, file, language, false);
		}

		/// <summary>
		/// Registers a client side javascript file include
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="file">The javascript include file to reference</param>
		/// <param name="language">The script's language</param>
		/// <param name="defer">Whether or not the script should be run after the page has fully loaded</param>
		public virtual void RegisterClientScriptFile(string key, string file, string language, bool defer)
		{
			StringBuilder block = new StringBuilder();
			block.Append("<script type=\"text/javascript\" language=\"");
			block.Append(language);
			block.Append("\" src=\"");
			block.Append(file);
			if (defer) block.Append(" defer=\"true\"");
			block.Append("\"></script>");

			if (!m_ClientScripts.ContainsKey(key))
			{
				m_ClientScripts.Add(key, block);
				//DbgTrace("Adding file: " + key + " - " + File);
			}
			else
			{
				m_ClientScripts[key] = block;
				//DbgTrace("Replacing file: " + key + " - " + File);
			}
		}

		/// <summary>
		/// Registers a client side javascript block. The block is automatically surrounded by &lt;script> tags
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="script">The javascript to include.</param>
		public override void RegisterClientScriptBlock(string key, string script)
		{
			RegisterClientScriptBlock(key, script, "Javascript", false);
		}

		/// <summary>
		/// Registers a client side javascript block. The block is automatically surrounded by &lt;script> tags
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="script">The javascript to include.</param>
		/// <param name="language">The script's language</param>
		public virtual void RegisterClientScriptBlock(string key, string script, string language)
		{
			RegisterClientScriptBlock(key, script, language, false);
		}

		/// <summary>
		/// Registers a client side javascript block. The block is automatically surrounded by &lt;script> tags
		/// </summary>
		/// <param name="key">Script key. If a script file is already registered using this key then the previous script is replaced</param>
		/// <param name="script">The javascript to include.</param>
		/// <param name="language">The script's language</param>
		/// <param name="defer">Whether or not the script should be run after the page has fully loaded</param>
		public virtual void RegisterClientScriptBlock(string key, string script, string language, bool defer)
		{
			StringBuilder block = new StringBuilder();
			block.Append("<script type=\"text/javascript\" language=\"");
			block.Append(language);
			block.Append("\"");
			if (defer) block.Append(" defer=\"true\"");
			block.Append("><!--\n");
			block.Append(script);
			block.Append("\n--></script>");

			if (!m_ClientScripts.ContainsKey(key))
			{
				m_ClientScripts.Add(key, block);
				//DbgTrace("Adding script: " + key + " - " + script);
			}
			else
			{
				m_ClientScripts[key] = block;
				//DbgTrace("Replacing script: " + key + " - " + script);
			}
		}

		public bool IsClientScriptRegistered(string key)
		{
			return m_ClientScripts.ContainsKey(key);
		}
		#endregion

		/// <summary>
		/// Called just before the page is rendered. All components within this page will
		/// have registered client scripts by now, so we take the chance to set the ClientScript
		/// property of the header control as the collective client script for this page.
		/// </summary>
		/// <param name="e"></param>
		protected override void OnPreRender(EventArgs e)
		{
			// We need to dump the client-side script into an ASP.NET Literal control
			// called "_clientScript". If this hasn't been added to the form then we
			// just create a dummy and set it as invisible.
			if (_clientScript == null)
			{
				_clientScript = new Literal();
				_clientScript.Visible = false;
			}
			else
				_clientScript.Text = ClientScript;

			base.OnPreRender(e);

//			if (Controls.Contains(_clientScript))
//				_clientScript.Text = ClientScript;
		}
	}
}