Notes From the Atlas Hands On Lab

Wednesday, September 21, 2005

Rough and random thoughts while playing with the new Atlas bits.

Lab 1

Lab 1 creates a master page with <atlas:script> tags to ensure links to the Atlas framework .js files are sent to the client. I’d like to see this functionality in a base class so it isn’t copy and pasted everywhere, or simply injected auto-magically, perhaps when an attribute like <% @ Page AtlasEnabled=”true” %> appears.

Nifty master page tricks: the master page uses a ContentPlaceHolder inside the %lt;head%gt; tag, which makes it easy for content pages to override the contents of head. The master page does not define a %lt;form> tag, but leaves the content pages to define the tag (typically with action=”” since there are no postbacks involved).

Glitch: the setup puts a default.master and a default.aspx in the same directory, which can produce duplicate definitions for _default in the codegen directory. The errors appear in temporary files with scary names, and the errors come and go depending on how many files compile. It’s scenarios like this that make the system appear broken and one reason why people hate the project-less web project.

Cool: you can generate JavaScript proxies for a web service by browsing to the asmx file and appending /js (why not ?js to be consistent with ?wsdl?). Assuming you wire up a button’s onclick event, you can pull back and process results with relatively simple code. Lab 1 passes the contents of a textbox to a HelloWorld type service, which essentially echoes the input back with a timestamp.

function DoSearch()

{

var SrchElem = document.getElementById("SearchKey");

Samples.AspNet.HelloWorldService.HelloWorld(

SrchElem.value, OnRequestComplete

);

}

function OnRequestComplete(result)

{

var RsltElem = document.getElementById("Results");

RsltElem.innerHTML = result;

}

Lab 2

Lab 2 performs the same work as Lab 1, but with a declarative syntax. Instead of writing JavaScript you write a mess of declarative XML that only a machine can love. Excerpt:

<serviceMethod

id="helloService"

url="HelloWorldService.asmx"

methodName="HelloWorld">

<binding dataContext="SearchKey" dataPath="text"

property="parameters" propertyKey="query" />

</bindings>

</completed>

</serviceMethod>

Weep: Lab 2 didn’t work for me immediately and I had to stare at the XML and compare the above to what was in the sample. Not knowing what else to do I started stepping through the Atlas JavaScript. I was deep inside a JSON.serialize method when I realized it was building a payload like “query:foo”, where “foo” was the value I typed into the textbox and “query” was the name of the web service parameter – except I had named my parameter on the C# method differently.

I hope that none of the XML cruft will have to be hand written. I hope there will be some way to keep the XML and web method in sync, or decoupled. Lab 1 worked because the JavaScript proxy was custom generated from the code– I hope something along those lines will be available for the declarative service method bindings.

Lab 3

Lab 3 added auto-completion to the textbox control, which I found rather appealing in a scary way. When typing into the textbox the JavaScript will invoke a web service method and bring back a list of possible matches to display in a DHTML control.

Unfortunately, this lab started throwing a JavaScript exception, so once more I tried to step through the optimized-for-transport-no-whitespace JavaScript of the framework. I thought my head was going to explode. I gave up and posted on the asp.net forums, and found that changing:

made everything work.

Sigh.