HTMLEditor Provider - How to write a custom provider for ASP.NET 2.0

/*
 * FCKeditor - The text editor for internet
 * Copyright (C) 2003-2006 Frederico Caldeira Knabben
 * 
 * Licensed under the terms of the GNU Lesser General Public License:
 * 		http://www.opensource.org/licenses/lgpl-license.php
 * 
 * For further information visit:
 * 		http://www.fckeditor.net/
 * 
 * "Support Open Source software. What about a donation today?"
 * 
 * File Name: fck_dialog_common.js
 * 	Useful functions used by almost all dialog window pages.
 * 
 * File Authors:
 * 		Frederico Caldeira Knabben (fredck@fckeditor.net)
 */

// Gets a element by its Id. Used for shorter coding.
function GetE( elementId )
{
	return document.getElementById( elementId )  ;
}

function ShowE( element, isVisible )
{
	if ( typeof( element ) == 'string' )
		element = GetE( element ) ;
	element.style.display = isVisible ? '' : 'none' ;
}

function SetAttribute( element, attName, attValue )
{
	if ( attValue == null || attValue.length == 0 )
		element.removeAttribute( attName, 0 ) ;			// 0 : Case Insensitive
	else
		element.setAttribute( attName, attValue, 0 ) ;	// 0 : Case Insensitive
}

function GetAttribute( element, attName, valueIfNull )
{
	var oAtt = element.attributes[attName] ;

	if ( oAtt == null || !oAtt.specified )
		return valueIfNull ? valueIfNull : '' ;

	var oValue ;
	
	if ( !( oValue = element.getAttribute( attName, 2 ) ) )
		oValue = oAtt.nodeValue ;

	return ( oValue == null ? valueIfNull : oValue ) ;
}

// Functions used by text fiels to accept numbers only.
function IsDigit( e )
{
	e = e || event ;
	var iCode = ( e.keyCode || e.charCode ) ;

	event.returnValue =
		(
			( iCode >= 48 && iCode <= 57 )		// Numbers
			|| (iCode >= 37 && iCode <= 40)		// Arrows
			|| iCode == 8						// Backspace
			|| iCode == 46						// Delete
		) ;

	return event.returnValue ;
}

String.prototype.trim = function()
{
	return this.replace( /(^\s*)|(\s*$)/g, '' ) ;
}

String.prototype.startsWith = function( value )
{
	return ( this.substr( 0, value.length ) == value ) ;
}

String.prototype.remove = function( start, length )
{
	var s = '' ;

	if ( start > 0 )
		s = this.substring( 0, start ) ;

	if ( start + length < this.length )
		s += this.substring( start + length , this.length ) ;

	return s ;
}

function OpenFileBrowser( url, width, height )
{
	// oEditor must be defined.
	
	var iLeft = ( oEditor.FCKConfig.ScreenWidth  - width ) / 2 ;
	var iTop  = ( oEditor.FCKConfig.ScreenHeight - height ) / 2 ;

	var sOptions = "toolbar=no,status=no,resizable=yes,dependent=yes" ;
	sOptions += ",width=" + width ;
	sOptions += ",height=" + height ;
	sOptions += ",left=" + iLeft ;
	sOptions += ",top=" + iTop ;

	// The "PreserveSessionOnFileBrowser" because the above code could be 
	// blocked by popup blockers.
	if ( oEditor.FCKConfig.PreserveSessionOnFileBrowser && oEditor.FCKBrowserInfo.IsIE )
	{
		// The following change has been made otherwise IE will open the file 
		// browser on a different server session (on some cases):
		// http://support.microsoft.com/default.aspx?scid=kb;en-us;831678
		// by Simone Chiaretta.
		var oWindow = oEditor.window.open( url, 'FCKBrowseWindow', sOptions ) ;
		
		if ( oWindow )
		{
			// Detect Yahoo popup blocker.
			try
			{
				var sTest = oWindow.name ; // Yahoo returns "something", but we can't access it, so detect that and avoid strange errors for the user.
				oWindow.opener = window ;
			}
			catch(e)
			{
				alert( oEditor.FCKLang.BrowseServerBlocked ) ;
			}
		}
		else
			alert( oEditor.FCKLang.BrowseServerBlocked ) ;
    }
    else
		window.open( url, 'FCKBrowseWindow', sOptions ) ;
}