AJAX

You've deployed your app in prod server, you run it on the browser and you get an exception:

[NullReferenceException: Object reference not set to an instance of an

	object.]
System.Web.Script.Services.WebServiceData.GetWebServiceData(Http

	Context context, String virtualPath, Boolean failIfNoData,

	Boolean pageMethods) +378
System.Web.Script.Services.PageClientProxyGenerator.GetClientProxy

	Script(HttpContext context, IPage page, Boolean debug) +45
System.Web.UI.ScriptManager.RegisterServices() +728   System.Web.

	UI.ScriptManager.OnPagePreRenderComplete(Object sender,

	EventArgs e) +244
System.Web.UI.Page.OnPreRenderComplete(EventArgs e) +2012740
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBef

	oreAsyncPoint, Boolean includeStagesAfterAsyncPoint)+1566

It happens when your site use ASP.NET AJAX RC in a VS 2005 Web Site Project and you deploy with "publish web site" or "web deployment project" utility with checkbox "allow the site to be updatable" unchecked.

It's a bug from ASP.NET AJAX RC1 and will be fixed in next version.

Until this you can make everything work fine if you precompile with checkbox "allow this site to be updatable" checked.

My primary idea for this post was how to use the small and beauty JSON format for data transfer in a windows mobile application. For that I use the infrastructure of AJAX. I implement a Webmethod in a classic ASPX page.

<script runat="server">

</script>

For calling the Method form the page (or from a webservice) i use a Winforms application and the httpwebrequest class. Then i call the URL following the method name. The second part is to use a specific content  type in header "application/json". To transfer complex data you have to build a json type. For my sample i used a simple string containing "test". The contextKey is a reserved word.

The result is in my sample also a string and can be passed to a textbox.

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim wRequest As HttpWebRequest = HttpWebRequest.Create("http://url/Default4.aspx/Nachladen1")

wRequest.Method = "POST"

wRequest.ContentType = "application/json; charset=utf-8"

wRequest.Headers.Add(HttpRequestHeader.Pragma.ToString, "no-cache")

Using writer As Stream = wRequest.GetRequestStream

Dim send As String

send = "{""contextKey"":""test""}"

Dim data As [Byte]() = Encoding.ASCII.GetBytes(send)

End Using

Dim WResponse As HttpWebResponse = CType(wRequest.GetResponse, HttpWebResponse)

Dim recieve As StreamReader = New StreamReader(WResponse.GetResponseStream())

Dim result As String = recieve.ReadToEnd.ToString

End Sub

Small nice and sexy!

AJAX

I have seen this asked a couple of times in the newsgroups hence this post. A simple way of refreshing an UpdatePanel using JavaScript is to add a HiddenField to the page, change its value using JS and then have the HiddenField raise a postback event.

The HiddenField causes the UpdatePanel to refresh because it has been declared as a trigger, is a child trigger or because the UpdatePanel.Update() method is called in the HiddenField ValueChanged event handler. The sample code shows these three scenarios.

Note: The HiddenField will obviously need to be registered as an async postback control (RegisterAsyncPostBackControl) if it is outside the UpdatePanel.

As you can tell I really love this VisualWebGui stuff from Guy Peled.  Take a look at the latest ability, its called "Dual Mode". Essentially you build your web site using their technology and you deploy to the Web normally, or deploy as a complete Windows Forms application!  Of course you will have to make special consideration for your business objects and more importantly your data source but its just damn cool.

I know I have been waiting for something like this for many, many years now. 

In ASP.NET AJAX, the Ajax Server Extensions consists of a powerful set of server controls that simulate Ajax behavior on the client. In other words, these controls do not perform Ajax in its traditional sense (JavaScript calls to a server and dynamic updates with dhtml) but rather in a different way that gives the same illusion to the end user.

To demonstrate the power of these controls, I've taken an existing ASP.NET application that suffered from normal, pre-ajax symptoms like page refreshes, static content and loss of interactivity and added the controls to make it a more engaging experience. The goals for the task were as follows:

• Improve network latency - cut back on the amount of data being passed back and forth between the server and browser
• Eliminate unnecessary page refreshes - keep the user connected to the application and the interaction as fluid as possible
• Keep UI and application logic on the server - This spares us from exposing ui logic to savvy web users (like yourselves) and also gives us the luxury of supporting the rare cases when a browser has JavaScript disabled
• Seamless and transparent integration - Keep intact the existing logic on the server and make integration as unintrusive as possible
• Stick to familiar paradigm - leverage the server controls as much as possible to provide the typical ASP.NET developer a familiar paradigm to work with

Along the way I also tried to exercise some common, recommended patterns for ASP.NET AJAX:

• Set UpdateMode for UpdatePanels to Conditional
• Placed ScriptManager in master page, leveraged ScriptManagerProxy for content pages
• Avoided gratuitous animations - kept animations subtle, relevant and simple
• Set Timer control interval to a high value - the timer actually runs on the client, we should be mindful of their resources

The application manages to use all of the controls in the AJAX Extensions (not the Futures CTP). For a little extra, it includes the AutoCompleteExtender for the search box. By the way, this control is now in the Ajax Control Toolkit - where it belongs.

The code for the application (written for the 1.0 release) can be downloaded here:  http://www.neudesic.com/uploads/david_barkol/ajaxserverextensions.zip  

Below is a snapshot of the application in action:

I just noticed that AJAX 1.0 has been officially released. Be sure to check out the website for more details: http://ajax.asp.net/.

Its out.  http://ajax.asp.net/

Now that Microsoft has released Atlas...sorry ASP.NET AJAX, lots and lots of applications are going to use it (many are already using it). Here is a simple but handy tool that I wrote using ASP.NET AJAX and the Control Toolkit.

BinaryIntellect Web Site File Manager is a FREE tool for managing files and folders of your web site. Just include the FileManager.aspx in your web site and that's it! You have a complete file manager ready. It supports almost all the file and folder management operations such as folder creation, cut, copy, paste, rename, delete and upload. You also get complete source code of the tool. Developed using ASP.NET 2.0 server controls, ASP.NET AJAX and ASP.NET AJAX Control Toolkit this tool is a must for any web site owner or host.

Download the tool at http://www.binaryintellect.net/products/displayproductdetails.aspx?productid=8

The UpdatePanelPopup Extender has been updated to use the ASP.net Ajax RTM version. I have also added an example that shows how to add/delete a record using the popup. Like before, we have a GridView and DetailsView setup using the standard Master/Details way. The only difference being that the DetailsView is "floating" and positioned at a location (top left icon) defined by the user using the custom extender. 

Download the latest version here.

Ajax is cool, for sure.  However sometimes its not so easy to work with, Ajax brings back a problem to web development that had been going by the wayside for a few years.  You see when I started back in early 2000, we had MS IE, Netscape 4, AOL and a slew of other browsers to support.  Writing interactive web programs for that collection of browsers was roughly akin to writing source code for multiple platforms.  Actually that's just what it is, i guess the analogy works too well.  ASP.NET made a lot of this much nicer, ok well in truth I worked on intranet based projects that locked into one browser.  So while the problem may not have gotten any better I couldn't see it ;)   All that changed a couple years ago, working on very public sites again they had to work in FF and IE, granted this is much better than the old browser collection.  So one problem i had yesterday was Firefox kept barking (rudely) about selectSingleNode() is not a function.  It sure is, its part of an xml element!  i said, but it persisted.  After much googling, i was able to write this function to wrap the functionality.  I'm sure there are better ways of doing this, but this is the one I found.  Judging by the amount of googling that i did to find the bits & parts, there are some out there with a similar problem.  I guess what i don't understand is why it takes three lines of code to do this in FF and only one in IE.  Is it that coming from an IE background my point of view is skewed?  Or is this just legitimately more difficult in FF?   I'll bet that most frameworks (atlas/etc..) have this built in and I just didn't see it.  Post a comment and tell me if that's it!

    function SelectSingleNode(xmlDoc, elementPath)
    {
        if(window.ActiveXObject)
        {
            return xmlDoc.selectSingleNode(elementPath);
        }
        else
        {
           var xpe = new XPathEvaluator();
           var nsResolver = xpe.createNSResolver( xmlDoc.ownerDocument == null ? xmlDoc.documentElement : xmlDoc.ownerDocument.documentElement);
           var results = xpe.evaluate(elementPath,xmlDoc,nsResolver,XPathResult.FIRST_ORDERED_NODE_TYPE, null);
           return results.singleNodeValue; 
        }
    }