Atlas

Using Atlas to act as a check on javascript calls

Jonas Bush — Wed, 16 Aug 2006 21:48:00 GMT

One of the things I've been working on is how to use Atlas web services to verify actions on the server. So the client requests to perform a particular action on the server, and if they don't have access to perform that action or the action fails (because a database is down, or something along those lines), I don't want the method on the client to continue executing.

The problem with that is that Atlas web service calls are asynchronous by nature (explained here and here). So I can't say something like this:

if(myService.myServiceCall() == true)
{
//do stuff
}

What I've come up with is this javascript object:

function webServiceRunner(webServiceFunction, returnFunction, returnParams)
{
var _returnFunction = returnFunction;
var _returnParams = returnParams;
var _webServiceFunction = webServiceFunction;

this.runService = function()
{
_webServiceFunction(onServiceComplete);
}

function onServiceComplete(result)
{
    var r = '_returnFunction(';
    for(var i = 0; i < _returnParams.length; i++)
    {
      r += '_returnParams[' + i.toString() + ']';
      if(i < returnParams.length - 1)
        r += ',';
    }
    r += ', result);';
    //alert(r);
    eval(r);
  }
}

This takes advantage of some of the nice (and dangerous) features of Javascript, the eval() statement, the arguments object, and function pointers. Eval() will let you create a string, like var s = 'alert(“hi“);'; - and then call eval(s); - the end result of which will be “Hi“ showing up in an alert box. The arguments object is created automatically for you in javascript inside of any function, and contains an array of all the arguments passed into that function.

So now I can instantiate and call this class like so:

<span class="CommandLink" onclick="testOne(this);">Testspan>

Assuming I have a webservice defined, as well as the proper Atlas script manager setup:

<atlas:scriptmanager id="scriptManager" runat="server">
<services>
<atlas:servicereference path="TestWebService.asmx" />
services>
atlas:scriptmanager>

[WebMethod]
public bool HasAccess()
{
return false;
}

What ends up happening inside the webServiceRunner is that the following string will be created:

_returnFunction(_returnParams[0], result);

Then that string is eval-ed, and my original testOne function is called, with the original sender object (from the original click), and the result parameter from the web service.

If this is confusing, post a comment or send me an email and I'll try and elaborate further. If you think this is silly or useless, leave a comment and explain why. :)

Repeaters, Checkboxes and UpdatePanels, Oh My!

Jonas Bush — Mon, 08 May 2006 21:08:00 GMT

I was working on some sample stuff that I'll be posting later and ran into a problem. I had 2 different update panels; inside one was just a div, inside the other one was a repeater. Inside the repeater I had a bunch of checkboxes, and when I checked/unchecked them, I needed the first update panel to be updated. This posed a couple of problems:

A checkbox doesn't have a CommandName property, and can't be used to trigger a Repeater's ItemCommand event

This I got around by declaring the event handler for the checkbox in the markup: OnCheckedChanged=”myCB_OnCheckedChanged”, and in the event handler I can cast the sender argument to a checkbox. The other problem:

An UpdatePanel's list of triggers can't include a control that's inside a template

Which means I can't say <atlas:ControlEventTrigger ControlID=”myCB” EventName=”myCB_OnCheckedChanged” />, since myCB doesn't actually exist at runtime. Instead, in myCB_OnCheckedChanged, I can just say: updatePanel1.Update(); and everything works fine.

Hope this helps...

Atlas and JSON

Jonas Bush — Mon, 03 Apr 2006 21:10:00 GMT

I just finished up some code that uses some other functionality of atlas. To sum up: Whoa! This may be available in AJAX.net or some of the other frameworks, but I was amazed at how easy this was:

I have a web service that returns a class, like so:

public class MyClass

{

public string MyString;

public int MyInt;

}

[WebMethod(true)]

public MyClass MyWebMethod()

{

//init MyClass here

MyClass myClass = new MyClass();

return myClass;
}

the beauty of it is, I have access to those fields in my javascript:

function callWS()

{

MyWebService.MyWebMethod(onComplete);

}

function onComplete(result)

{

alert(result.MyString);
}

Very very very very cool :)

Success!

Jonas Bush — Wed, 15 Feb 2006 18:18:00 GMT

After struggling with Atlas for awhile, we finally released our latest feature on http://www.squeet.com. The new “Preview“ functionality uses the Atlas UpdatePanel to display the 5 latest entries for any blog you enter. It will by default show only a summary of the item, but you can click on the “expand“ link to show the full HTML content for the entry.

The UpdatePanel is surrounding a standard ASP.Net repeater control, which contains some LinkButtons. The UpdatePanel responds to the RowCommand event raised by the repeater, and all the code to handle the event is normal code-behind code. The Atlas portion of this portion was very easy to implement (once I got away from using the WebService calls directly, those don't seem to be fully mature yet).

Atlas, Viewstate, IE and FF.

Jonas Bush — Mon, 13 Feb 2006 14:47:00 GMT

In my inaugural post, I described a problem I had with a WebMethod erroring out instantly on the client, accompanied by a puzzling message in the Event Log, regarding viewstate.

On a whim, on that site, I decided to “publish” the website from within VS 2005 to a separate directory. I set up another virtual directory within IIS to point to that directory, loaded up the site and IE, and all my WebMethod calls were working!

From IE6, that is.

From FireFox, none of the calls work on the published website....

...the first time. If I click on the link that calls the WebMethod again (after getting the instant error), it works fine. Very weird.

Putting the hair back in.

Jonas Bush — Mon, 13 Feb 2006 14:07:00 GMT

In this post, I mentioned tearing my hear out because I couldn't get a gridview to work right with the update panel. Today I decided to just start on a fresh web form and everything seems to be working fine.

I did learn that an updatepanel without any triggers will consume any server-side event that fires inside of it (ie, to get paging and sorting working you don't need to explicitly specify triggers to handle those events). I also learned that (and this isn't related to Atlas) a gridview's page and sort events also fire off RowCommand events...which I guess make sense since the header is a “row” and the pager thing is also a “row”.

Still trying to figure out the updatePanel inside of a userControl thing figured out, I'll keep you posted.

Tearing my hear out, bit by bit.

Jonas Bush — Sun, 12 Feb 2006 17:07:00 GMT

Ok, I'm about to have a nervous breakdown and need to post this, and then walk away for a bit.

I have a gridview on a page, that looks like this:

<asp:gridview id="gvTest" runat="server" allowpaging="true" allowsorting="true" autogeneratecolumns="false" pagesize="5" onpageindexchanging="gvTest_PageIndexChanging" onrowcommand="gvTest_RowCommand" onsorting="gvTest_Sorting" enablesortingandpagingcallbacks="false">
<columns>
  <asp:boundfield datafield="Id" headertext="Id" sortexpression="Id" />
  <asp:boundfield datafield="Name" headertext="Name" sortexpression="Name" />
  <asp:templatefield headertext="Preview">
   <itemtemplate>
    <asp:linkbutton id="linkPreview" runat="server" commandname="Preview" commandargument='<%#(int)DataBinder.Eval(Container.DataItem, "Id") %>' text="Preview" />
   </itemtemplate>
  </asp:templatefield>
</columns>
</asp:gridview>

I have an UpdatePanel that has triggers like this:

Why then, when I sort or page the gridview, does the updatepanel swallow my postback, but when I click the linkbutton that says preview, do I get a postback?

Atlas - Jan CTP issues

Jonas Bush — Sun, 12 Feb 2006 16:13:00 GMT

I've been playing around with Atlas since the Jan CTP dropped a couple days ago. It's got some impressive functionality, as well as some (seemingly) glaring oversights. One of the things I'm trying to do is incorporate an UpdatePanel inside of a UserControl. I need the UpdatePanel to have a trigger that's on the containing page, but I can't get it to work. I've tried the following (on the containing page):

protected override void OnPreInit(EventArgs e)
{
ControlEventTrigger t = new ControlEventTrigger();
t.ControlID = this.linkGetFeedPreview.ID;
t.EventName = "Click";
previewControl.UpdatePanel.Triggers.Add(t);
base.OnPreInit(e);
}

I've also tried putting this code in OnInit, and have had no luck. I always get the error message The ControlID property of the trigger must reference a valid control. Has anyone else tried this and gotten it to work.

Another issue I've been having is that calls to a WebMethod in my page class aren't always executing. The javascript is: PageMethods.SomeMethodName(blah, onComplete, onTimeout, onError);. Many times when I execute that javascript, the error method immediately executes, and in the event viewer on that machine I'll see the following:

Event code: 4009

Event message: Viewstate verification failed. Reason: Viewstate was invalid.

Google has proven useless thus far. Anyone have any thoughts?