|
<h2><img border="0" src="scriptregister/scriptregister.GIF" width="431" height="241"></h2>
<h2>Introduction</h2>
<p>One of the things that drove me nuts while writing web applications was the
battle to modularise your code while still keeping generated HTML neat. In
particular, having individual code modules within a page render their own
javascript often resulted in pages containing many different and unrelated
pieces of script scattered in no particular order. It's nice to have javascript
appear within the <code>HEAD</code> tags of a page, where appropriate, but ASP
3.0 didn't provide a solution.</p>
<p>ASP.NET does provide a solution, of sorts, in the form of <code>
RegisterClientScriptBlock</code> method in the <code>Page</code> class. This
allows you to register blocks of client-side script that will, at page render
time, be output in one neat chunk to the page. I say it's a solution "of sorts"
because while it's a neat idea, it doesn't actually do what you would always
hope. </p>
<p>The issues, at least for me, of the <code>RegisterClientScriptBlock</code>
method were that the script is output after the opening <code>Form</code> tag of
an ASP.NET page. What if you don't have such a tag in your page? What if you
want the script output in the HEAD section instead? The method also required you
to include the <script> tags. To me just meant lots of repeated boiler plate
code and potential for mistakes. I wanted something that would make it easy to
include script from many different points within the page creation logic and
from within controls contained by a page. I also wanted a method that would fill
in the boiler plate code for me whereever possible.</p>
<h2>A new base class for your webpages.</h2>
<p>With ASP.NET allowing the ability to derive your pages from whatever <code>
System.Web.UI.Page </code>derived class you wish, there will no doubt be a
plethora of web page base classes available. I could have chosen to encapsulate
the functionality I needed in a separate utility class which would then be
instantiated and called from your own <code>System.Web.UI.Page</code> derived
class, but I'm lazy and so that particular exercise has been left to the reader.</p>
<p>I instead created a simple class, <code>BasePage</code>, derived from <code>
System.Web.UI.Page</code> from subsequent pages can be derived. The methods
available are:</p>
<h4>RegisterClientScriptBlock</h4>
<p>Registers a client side javascript block. The block is automatically
surrounded by <script> tags</p>
<pre>void RegisterClientScriptBlock(string key, string script)
void RegisterClientScriptBlock(string key, string script, string language)
void RegisterClientScriptBlock(string key, string script, string language, bool defer)</pre>
<h4>Parameters</h4>
<blockquote>
<p>key - Script key. If a script file is already registered using this key
then the previous script is replaced<br>
script - The javascript to include.<br>
Language - The script's language. Default is "Javascript"<br>
defer - Whether or not the script should be run after the page has fully
loaded. Default is false</p>
</blockquote>
<h4>RegisterClientScriptFile</h4>
<p>Registers a client side javascript file include</p>
<pre>void RegisterClientScriptFile(string key, string file)
void RegisterClientScriptFile(string key, string file, string language)
void RegisterClientScriptFile(string key, string file, string language, bool defer)</pre>
<h4>Parameters</h4>
<blockquote>
<p>key - Script key. If a script file is already registered using this key
then the previous script is replaced<br>
file - The javascript include file to reference<br>
Language - The script's language. Default is "Javascript"<br>
defer - Whether or not the script should be run after the page has fully
loaded. Default is false</p>
</blockquote>
<h4>RegisterClientScriptEvent</h4>
<pre>void RegisterClientScriptEvent(string key, string eventName, string ctrlName, string script)
void RegisterClientScriptEvent(string key, string eventName, string ctrlName, string script, string language)</pre>
<p>Registers a client side javascript event handler. Will be rendered only for
IE 4.0 and above.</p>
<h4>Parameters</h4>
<blockquote>
<p>key - Script key. If a script file is already registered using this key
then the previous script is replaced<br>
eventName - The event to handle<br>
ctrlName - The name of the HTML element(s) to apply this handler to<br>
script - The script to run<br>
Language - The script's language. Default is "Javascript"</p>
</blockquote>
<h4>IsClientScriptRegistered</h4>
<p>Returns <b>true</b> if the script block is registered; otherwise, <b>false</b>.</p>
<pre>public bool IsClientScriptRegistered(string key)</pre>
<h4>Parameters</h4>
<blockquote>
<p>key - Script key.</p>
</blockquote>
<h2>Using the class</h2>
<p>Using the class is simple. </p>
<ol>
<li>Include the <i>ScriptPage.cs</i> file in your project<br>
<br>
</li>
<li>Derive your page from <code>CodeProject.ScriptPage </code>instead of
<code>System.Web.UI.Page</code>.
<pre>namespace CodeProject
{
/// <summary>
/// Summary description for WebForm1.
/// </summary>
public class WebForm1 : CodeProject.ScriptPage
{
...</pre>
<li>
Include an ASP.NET Literal control named <code>_clientScript</code> at the place
within your page where you want the script to be rendered. This can be anywhere
on the page, but within the <code><HEAD></code> section is recommended.
<pre><HTML>
<HEAD>
<title>WebForm1</title>
<b> <asp:literal id="_clientScript" runat="server"></asp:literal></b>
</HEAD>
<body>
<form id=Form1 ...</pre>
<p><b>Important:</b> If you don't include this control then the javascript will not be rendered.
<br><br>
<li>To register some javascript from within a page simply call the base class'
methods:
<pre>
private void Page_Load(object sender, System.EventArgs e)
{
// Let's add some javascript
RegisterClientScriptBlock("Script1", "alert(\"Script1 called\");");
RegisterClientScriptFile("Script2", "MyScripts.js", "Javascript 1.2");
RegisterClientScriptEvent("Script3", "onclick", "MyButton", "alert(\"Script3 called\");");
}
</pre>
<li>
To register some javascript from within a user or custom control simply cast the parent page to
the base class and again call the base class' methods:
<pre>
CodeProject.ScriptPage basePage = Page as CodeProject.ScriptPage;
if (basePage != null)
basePage.RegisterClientScriptBlock("Script4",
"document.getElementById(\"MyTable\").style.backgroundColor = '#ff9900';",
"Javascript", true);</pre>
</ol>
<h2>Results</h2>
<p>Consider the page below which contains a simple form and a simple User Control. Both the form and the user control will register some javascript as described above.
<pre lang="asp.net">
<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="CodeProject.WebForm1"
enableViewState="False" Trace="False"%>
<%@ Register TagPrefix="CP" TagName="WebUserControl1" Src="WebUserControl1.ascx" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<asp:literal id="_clientScript" runat="server"></asp:literal>
</HEAD>
<body>
<form id=Form1 method=post runat="server">
<p>This is a very simple webpage. Click 'View Source' to
see the Javascript embedded within this page.
<P><input type=button id=MyButton name=MyButton value="Click me"></P>
<P><CP:WebUserControl1 id=WebUserControl11 runat="server"></CP:WebUserControl1></P></form>
</body>
</HTML></pre>
<p>The output, when rendered, is as follows:
<pre lang="html">
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<script type="text/javascript" language="Javascript 1.2" src="MyScripts.js"></script>
<script type="text/javascript" language="Javascript"><!--
alert("Script1 called");
--></script>
<script type="text/javascript" language="Javascript" defer="true"><!--
document.getElementById("MyTable").style.backgroundColor = '#ff9900';
--></script>
<script type="text/javascript" language="Javascript" for="MyButton" event="onclick" defer="true"><!--
alert("Script3 called");
//--></script>
</HEAD>
<body>
<form name="Form1" method="post" action="WebForm1.aspx" id="Form1">
<input type="hidden" name="__VIEWSTATE" value="/wEQBQg0MzYwOTMxOWRk16k9eelhvHlDer9mNoFRa/lCEqA=" />
<p>This is a very simple webpage. Click 'View Source' to
see the Javascript embedded within this page.
<P><input type=button id=MyButton name=MyButton value="Click me"></P>
<P>
<table id=MyTable name=MyTable border=1 width=200 height=60 bgcolor=grey>
<tr><td align=center valign=middle><font size=2 face=verdana>This is a User Control</font></td></tr>
</table></P></form>
</body>
</HTML></pre>
|
By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.
If a file you wish to view isn't highlighted, and is a text file (not binary), please
let us know and we'll add colourisation support for it.
Chris Maunder is the co-founder of
CodeProject and
ContentLab.com, and has been a prominent figure in the software development community for nearly 30 years. Hailing from Australia, Chris has a background in Mathematics, Astrophysics, Environmental Engineering and Defence Research. His programming endeavours span everything from FORTRAN on Super Computers, C++/MFC on Windows, through to to high-load .NET web applications and Python AI applications on everything from macOS to a Raspberry Pi. Chris is a full-stack developer who is as comfortable with SQL as he is with CSS.
In the late 1990s, he and his business partner David Cunningham recognized the need for a platform that would facilitate knowledge-sharing among developers, leading to the establishment of CodeProject.com in 1999. Chris's expertise in programming and his passion for fostering a collaborative environment have played a pivotal role in the success of CodeProject.com. Over the years, the website has grown into a vibrant community where programmers worldwide can connect, exchange ideas, and find solutions to coding challenges. Chris is a prolific contributor to the developer community through his articles and tutorials, and his latest passion project,
CodeProject.AI.
In addition to his work with CodeProject.com, Chris co-founded ContentLab and DeveloperMedia, two projects focussed on helping companies make their Software Projects a success. Chris's roles included Product Development, Content Creation, Client Satisfaction and Systems Automation.