The OnInit method

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protected override void OnInit(EventArgs e)
{
    base.OnInit(e);

// Without this one our control will throw an EXCEPTION in the design view of Visual Studio!!!!
    if (DesignMode)
        return;

// Ensuring the control is being registered
    // This is the absolute most important point in your Custom Control.
    // If you don't do this, no JavaScript from Gaia will be registered
    // In addition it will be IMPOSSIBLE to call ControlMethods on your 
    // control!!
    // Do this HERE!!
    Manager.Instance.RegisterPage(this.Page, this);

if (ShouldRender)
    {
        // Gaia LIBRARY stuff...
        Manager.Instance.AddInclusionOfCommonFiles();
        Manager.Instance.AddInclusionOfFileFromResource(
            "Gaia.WebWidgets.LibraryScripts.builder.js", 
            typeof(Manager), 
            "Builder");
        Manager.Instance.AddInclusionOfFileFromResource(
            "Gaia.WebWidgets.LibraryScripts.controls.js", 
            typeof(Manager), 
            "Ajax.InPlaceCollectionEditor");
        Manager.Instance.AddInclusionOfFileFromResource(
            "Gaia.WebWidgets.LibraryScripts.dragdrop.js", 
            typeof(Manager), 
            "Element.offsetSize");

// Our stuff
        Manager.Instance.AddInclusionOfFileFromResource(
            Page.ClientScript.GetWebResourceUrl(
                typeof(Dice),
                "SampleCustomControl.Dice.js"), 
                typeof(Dice), 
                "SampleCustomControl.Dice");
    }

// In addition we RE create our 
    // injector here since it might have been modified during the 
    // Persist process of our ViewState object
    // This is the actual instance being USED, the one created in our 
    // constructor is basically just tossed away!!
    itsInjector = new WebControlPropertyInjecter();

// Then we need to include any JavaScript resource files...
    // This must be done AFTER the RegisterPage process...!!
    // If you get funny JavaScript errors and you know there's 
    // no "syntax error" in your JavaScript 
    // the reason might be because you've "forgotten" to call 
    // Manager.RegisterPage or you've put this on
    // BEFORE your RegisterPage part...!!
    // It's imperative that all JavaScript files are included in "the 
    // right order" since we're using prototype inheritance in
    // the library...!!
    if (!Manager.Instance.IsAjaxCallback)
    {
        // This is standard ASP.NET inclusion of WebResource logic...
        // When microsoft created the RegisterClientScriptInclude and 
        // the GetWebResourceUrl methods
        // they didn't do it very "intuitive"...
        // A couple of difficulties is "figuring out the namespace" of 
        // the JavaScript file to 
        // include...
        // Tha basic rule is "use the default namespace of your 
        // library", "add up the name of any directories your .js file 
        // resides within"
        // and "then add the EXACT NAME of your JavaScript file" ...
        // All separated by "."s...
        // So if my .js file was within the "JavaScript" directory I 
        // had to add up ".JavaScript" just before the ".Dice.js" 
        // part...!!!!
        // Source of frustration for MANY ASP.NET developers...!!
        // Not our fault, blame Microsoft ;)
        // The easiest way to ensure you're doing it the right way is 
        // to REMOVE EVERYTHING in your JavaScript file
        // and just put an "alert('q')" or something inside it and 
        // develop until you see a popup box appear
        // when you go to the page your control is in...!!
        //
        // VERY IMPORTANT!
        // The string inclusion of your JavaScript file should also 
        // match 100% the string you're using in your
        // "assembly: WebResource" attribute...!!
        // (See the TOP of this file!!)
        //
        // In addition it's VERY IMPORTANT that your JavaScript file is 
        // marked as "Embeded Resource" in the properties of it.
        // Mark your JavaScript file in the Solution Explorer and 
        // rightclick and choose "Properties" and set it to "Embedded 
        // Resource"...!!

Page.ClientScript.RegisterClientScriptInclude(
            "SampleCustomControl.Dice.js",
            Page.ClientScript.GetWebResourceUrl(typeof(Dice),
            "SampleCustomControl.Dice.js"));
    }
}

As you can see here the most important parts are that we must make sure our JavaScript file is included. Another very important part is that we register our control by calling the Manager.Instance.RegisterPage method. Without this method call our control will just be a "normal" WebControl and not a Gaja Ajax control!
A couple of other interesting parts is that we include the common Gaia JavaScrip files, for us that means builder.js, controls.js and dragdrop.js. (from ScripAculous)
In addition the AddInclusionOfCommonFiles method will include the "fundamental" files which ALL Gaia Ajax Controls needs. Basically this ensures inclusion of the prototype.js, Control.js and the WebControl.js which are the JavaScript base classes in Gaia. (in addition to the prototype library)
In addition we toss away the existing WebControlProertyInjector object and creates a new since all changes done in it up till now are basically just the changes done while serializing to and from the .aspx file definitions.
Also the observant reader might have noticed some "funny parameter" to our include JavaScript method. The last parameter of e.g. the RegisterClientScriptInclude method is actually a JavaScript type and this type ensures we have loaded the complete JavaScript file before we try to use types from it. It is only used when we include JavaScript files in Ajax CallBacks! Basically it's a safety hatch to ensure that he whole JavaScript file have been loaded before we try to execute code from within it!

Continue to the JavaScript file