Tag / Ajax

by Aaron

Disabling automatic Sys.UI.Control attachment

If you’re using the Microsoft Ajax Library (learn), you may not always want to start the automatic “attach” process that takes place when the page loads. It’s easy to disable, but not yet documented any place I could find easily. 

<script src="Scripts/MicrosoftAjax/Start.debug.js" type="text/javascript"></script>
<script type="text/javascript">

    var ajaxPath = "";

    Sys.activateDom = false;

All you must do is set Sys.activateDom to false as shown above (make sure this is set after the new Start.js JavaScript file loads, otherwise your code will crash when you try to set the Sys object before it has been properly constructed).

Then, to begin the attach process, just call Sys.activateElements: 

Sys.activateElements(document.documentElement);

In the code line above, though I’ve specified that I want the entire HTML document activated, you could provide any element you want as a starting point (for example to optimize the use of the library and prevent unnecessary DOM searching for example).

I’m adding the delay in some JavaScript code because I wanted to set up a few variables in advance of the attach occurring. I tend to write my JavaScript code in an object oriented fashion these days (using the prototype pattern), including code that is interacting with the DOM. In this case, I’ll create a class that represents the logic of the page rather than following the typical purely functional model that is done on many JavaScript pages. But, when using the “eval” syntax of the Microsoft Ajax library “{{ code }}”, occasionally, I’ll need to delay the eval or the page will crash.

From my recent post on making a simple command extension to the Microsoft Ajax library, I wanted to make that more object oriented by referring to an instance of my class, rather than pointing directly to a function: 

<body sys:attach="wpc" 
    wpc:onbubbleevent="{{$view.onCommand}}"  
    xmlns:sys="javascript:Sys" xmlns:wpc="javascript:WiredPrairie.Commanding">

$view represents the instance of my page’s behavior. However, if the attach were to occur too early, this variable is not yet set. I’m using the slick script loading functionality of the ajax library, specifying the various JavaScript libraries and their dependencies, including my page’s behavior. It’s not until that JavaScript code is loaded that the code can create an instance – and that could be AFTER the page has already done the attach logic. The attach happens before Sys.onReady for example. (Sys.onDomReady happens before onReady, but not all JavaScript files may have been downloaded). 

Sys.onReady(function() {
    $view = new WiredPrairie.MainView();
    
    Sys.activateElements(document.documentElement);

When using the sys:attach attribute, note that the attach and instantiation process happens before any code you’ve specified in onReady is executed (Microsoft currently uses the same method for determining when everything is ready by adding a function call to onReady – but their call is first in the queue).

by Aaron

Microsoft Ajax Library Declarative Command Alternatives

There may be another way to accomplish this, but I wanted to have a simple commanding system in the Microsoft Ajax Library which worked outside of the templates.

After a number of false starts and frustration brought about by very limited documentation, I discovered a reasonable implementation.

I created a script file, “Commanding.js” (in a Scripts folder):

/// <reference name="MicrosoftAjax.js"/>

Type.registerNamespace("WiredPrairie");

WiredPrairie.Commanding = function(element) {
    WiredPrairie.Commanding.initializeBase(this, [element]);
}

WiredPrairie.Commanding.prototype = {
    initialize: function() {
        WiredPrairie.Commanding.callBaseMethod(this, 'initialize');

        // Add custom initialization here
    },
    dispose: function() {
        //Add custom dispose actions here
        WiredPrairie.Commanding.callBaseMethod(this, 'dispose');
    }
}

WiredPrairie.Commanding.registerClass('WiredPrairie.Commanding', Sys.UI.Control);

if (typeof (Sys) !== 'undefined') Sys.Application.notifyScriptLoaded();

This is just a basic JavaScript class, with the default implementation provided by the Ajax Client Control template in Visual Studio 2008. The reason this is needed is that Controls all support a special event onBubbleEvent that is needed by commands when they’re raised.

In the body of the HTML, I attached an instance of the “WiredPrairie.Commanding” class to the body. Next, I attached a JavaScript function to the onbubbleevent (wpc:onbubbleevent, remember that all attributes need to be all lowercase). Here, I’ve used the special {{ }} syntax to indicate I want JavaScript code to execute when the event is raised. 

<body xmlns:sys="javascript:Sys" 
    xmlns:wpc="javascript:WiredPrairie.Commanding" 
    sys:attach="wpc" 
    wpc:onbubbleevent="{{onCommand}}" >
    <div >
        <button sys:command="startRunningCommand" sys:commandargument="iargueaboutit">Run</button>
    </div>
</body>

I needed my JavaScript WiredPrairie.Commanding class to load and run at the right time on the page, so I’ve used the new loader classes in the Ajax library. 

Sys.loader.defineScripts(null, [
{
    name: "Commanding"
    ,releaseUrl: "Scripts/Commanding.js"
    ,debugUrl: "Scripts/Commanding.js"
    ,dependencies: ["ComponentModel"]
 }
 ]);

First, I needed to declare this new script file and any dependencies. Since I don’t yet have a minified version, I’ve just specified the same file for the releaseUrl and the debugUrl. For the dependencies property, I looked through a few source files to discover that the “ComponentModel” key included Sys.UI.Control, which my class depends on to be created, so I added that here (hopefully this will be documented at some point).

Next, I added code to indicate to the loader which scripts were necessary and let it determine the best way to load them: 

Sys.require([Sys.components.dataView, Sys.scripts.jQuery,
 Sys.scripts.Commanding]);

Here, you see the “Commanding” key is added to a special namespace, “Sys.scripts.”

In the new onReady event which is raised when the DOM and scripts have been loaded, I’ve added code to activate the control class I wrote: 

Sys.onReady(function() {
    Sys.activateElements(document.documentElement);    
});

Finally, I wired up that event declared above in the onbubbleevent attribute on the body element. 

function onCommand(sender, args) {
    if (typeof (args) !== "undefined") {
        var commandName = args.get_commandName();
        var commandArgument = args.get_commandArgument();
        alert(commandName + " " + commandArgument);
    }
}

OK, that’s cool, but you might want to raise a command without it being triggered by a control event (such as a click). So, I added a simple function to my Commanding class: 

WiredPrairie.Commanding.raiseCommand = function(sender, commandName, commandArgument, commandSource) {
    var source = sender || document.body;
    Sys.UI.DomElement.raiseBubbleEvent(source, new Sys.CommandEventArgs(commandName, commandArgument, commandSource));
}

var $sendCommand = WiredPrairie.Commanding.raiseCommand;

Because of the way the raiseBubbleEvent works, it does depend on the source being set to a valid control/element (as raiseBubbleEvent walks through the parent chain until there aren’t any more parents) – in this case, I’ve defaulted to the body element.

Finally, an enhancement to the test case above to demonstrate both receiving and sending a command: 

function onCommand(sender, args) {
    if (typeof (args) !== "undefined") {
        var commandName = args.get_commandName();
        var commandArgument = args.get_commandArgument();
        switch (commandName) {
            case "startRunningCommand":
                $sendCommand(null, "alertCommand", new Date().toLocaleTimeString(), null);
                break;
            case "alertCommand":
                alert(commandArgument);
                break;
            default:
                break;
        }
    }
}

One command just sends another command which displays an alert. It’s simple, but functional.

Enjoy.