Most people coming to ASP.NET MVC tend to have similar problems. Most of them are related to refreshed understanding of HTML+HTTP limitations. Some are mitigated by ASP.NET MVC (checkboxes), but a lot require custom solutions.

One of the more common problems I get asked about by every second person learning MVC is how to make a form with two independent submit buttons, where both should submit the same data, but a have a different processing logic. For example, form may have a Save Draft button and Publish button.

Until now, I always said that it is possible, Google/StackOverflow and find out. But I just had to build such kind of thing myself, so I finally took some time to find/build the final solution.

So, let’s look at the solutions available online.

StackOverflow question “How do you handle multiple submit buttons in ASP.NET MVC Framework?” is the starting point, but it does not provide a good solution for the situation where you need to send same data for both buttons, except the solution to switch by button name, which is duct-taping.

Post “ASP.NET MVC – Multiple buttons in the same form” by David Findley is much more interesting, since his AcceptParameterAttribute is very similar to my solution. However, this has several (small) shortcomings: first, you have to specify what is actually an action you want to do in an attribute. So even if you name your action “SaveDraft”, you will still need to specify AcceptParameter(Name=“button”, Value=“saveDraft”). Another thing is need to put [ActionName] on your actions, which is understandable, but a bit confusing for people who do not yet know the idea.

So, I wanted to build the solution that would require at most one attribute, and where the name of action method corresponds to the attributes of the button. Also, since <input> value is the thing being shown in the button, and <button> value has issues in IE, I decided to go with name attribute and ignore value completely (which seems to be consistent with David Findley’s commenters).

Now, the solution. Basically, instead of using ActionMethodSelectorAttribute, I am using ActionNameSelectorAttribute, which allows me to pretend the action name is whatever I want it to be. Fortunately, ActionNameSelectorAttribute does not just make me specify action name, instead I can choose whether the current action matches request.

So there is my class (btw I am not too fond of the name):

public class HttpParamActionAttribute : ActionNameSelectorAttribute {
    public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo) {
        if (actionName.Equals(methodInfo.Name, StringComparison.InvariantCultureIgnoreCase))
            return true;

        if (!actionName.Equals("Action", StringComparison.InvariantCultureIgnoreCase))
            return false;
        
        var request = controllerContext.RequestContext.HttpContext.Request;
        return request[methodInfo.Name] != null;
    }
}

How to use it? Just have a form similar to this:

<% using (Html.BeginForm("Action", "Post")) { %>
  <!— …form fields… -->
  <input type="submit" name="saveDraft" value="Save Draft" />
  <input type="submit" name="publish" value="Publish" />
<% } %>

and controller with two methods

public class PostController : Controller {
    [HttpParamAction]
    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult SaveDraft(…) {
        //…
    }

    [HttpParamAction]
    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Publish(…) {
        //…
    }
}

As you see, the attribute does not require you to specify anything at all. Also, name of the buttons are translated directly to the method names. Additionally (I haven’t tried that) these should work as normal actions as well, so you can post to any of them directly.

There is some room for improvements (hardcoded “action” as a default action name), but in general I’m satisfied with this solution.

According to HTML5 spec, every attribute that starts with data- should be ignored by browser and considered a data needed for some scripts. For example:

<ul data-sortable="yes">…</ul>

Does it remind you of something? It is a simplified version of XML namespaces, but limited to non-hierarchical data and with much more probability of data clash.

John Resig, in the comments to his blog post on the matter, says that “The learning curve and failure rate are too high to purely XML-based markup, which is why the data-* attribute exists as a means to implementing this solution”. I completely disagree with the learning curve argument, and this is why:

Programming is complex.

It is easy to forget about the complexity while doing smart new stuff. And new cool things is not what I am talking about. Inventing new thing is easy, since you do not have to think about all limitations of the new ones. Making them work for all occasions, that is what is complex.

It is easy to praise HTML5 over XHTML. It is easy to praise microformats.

But all standards are here for a reason. It is easy to punch Microsoft, however first versions of Google’s Picasa didn’t support non-English text in labels, at all. Current version of Adobe Buzzword does not support Russian text. Current versions of Picasa and Opera do not support Drag&Drop outside of application. I have never seen any of such problems in MS applications. In fact, Visual Basic supported Unicode for ages, while relatively modern web languages stumble on it.

I have already blogged about microformats being a hack. And now I read about BBC removing microformats support due to problems with screen readers and semantics of abbr tag. Is it easy to remember that screen readers must be supported? No. Is it a shiny 2.0 kind-of-thing to think about them? No. But it is one of the multiple things you have to think about when making a wide-used standard.

Adding easy solutions when possible is a great thing. But it wrong to think of programmers as people who can only work with easy solutions. Flexibility is much more important than ease of use, and that’s the lesson that produced, for example, ASP.NET MVC. Also, easy ways should exists as shortcuts for flexible ones, not be orthogonal to them.

And while HTML may be about design, and text processing, and other things, data-* is about programming.

Google Chrome — short thoughts

September 2nd, 2008

This may belong to Twitter.

  1. Comic — nicely done, but how about some good words for work of other people (especially when influenced by it)?

    IE8

    • Process per tab
    • Private mode
    • Emphasis of domain name in the address bar

    Opera

    • Search shortcuts
    • Speed dial (but Google improved it)
    • Tabs on top of address bar (which is the sane way to do it)

    Firefox

    • Search/address bar 
    • JavaScript JIT (Firefox 3.1)

    I understand why Microsoft is not saying “just like Firefox”, however a lot of Google PR is about being friendly.

    Also, I was a bit surprised by the multiple references to tab crashes not crashing the application. Does somebody really encounter often tab crashes? Opera crashes in extremely rare cases, and it is possible to restore a session anyway.

  2. Future? I still use Google Talk (and converted a lot of people), but it seems no one at Google cares anymore. There are at least three different Google Talk editions, with unrelated features (Labs Edition supports text conferencing, but not file sending).

    So it is interesting if Google is going to support Chrome if it does not get significant popularity. It is open-source, however, so my concerns may not prove important.

  3. Process explorer is a fabulous feature, a must have for every other browser. However, aside from that, a good JavaScript debugger is important.

  4. Chrome is a bit of a performance hog, not sure how it compares to Firefox, but it is definitely heavier than Opera, especially CPU-wise.

  5. Not exactly Chrome-related, but why people seem to want a relational database in the browser (Gears, HTML5)? JavaScript structures are already extremely usable and easy to work with. They also abstract fast searching (hashes). Why not use a JSON storage stored in a browser-specific way, instead of putting SQL specification into HTML?

In general, Chrome may replace Opera for me, depends on how well it works with saved passwords (Firefox is way worse than Opera’s Wand), gestures and its overall performance.

Coming from a vacation, I have just discovered a new ASP.NET AJAX roadmap. A post by Matt Berseth starts with a summary of discussion done so far.

I have some personal opinions on the question of ASP.NET AJAX since our team worked with it a lot. So I decided to write a post instead of just commenting existing discussion.

I think I have a slightly different approach to this framework, as compared to other posters. I do not have to choose jQuery/prototype/mootools over ASP.NET AJAX. It is obvious that chaining in jQuery makes life easier, and extending element whenever possible is also a friendly approach.

However, I will still use ASP.NET AJAX for the interoperability with ASP.NET architecture — I can have a JavaScript part for any control I have, and pass values between C# and JavaScript. Also the component lifecycle (being able to handle component references easily) is a large win for me.

What I do not like is the cumbersome get_/set_ requirement without a built-in shortcut (I described one solution earlier) and cumbersome event subscription.

Event Subscription

So, let’s start with this roadmap sample:

   1:  $query("textarea.rich")
   2:    .addHandler("focus", function(e) {
   3:      Sys.Debug.trace("focused into " + (e.eventTarget.id || "?"));
   4:    })
   5:    .setStyle("width", function() {
   6:      return (document.body.clientWidth – 10) + "px";
   7:    })
   8:    .create(Contoso.UI.RichTextBehavior, {
   9:      showToolbar: true,
  10:      fonts: ["Arial", "Times", "Courier"]
  11:    });

What we have now in our project for event subscription is similar to this

   1:  with (Auto.Events) {
   2:    when(textarea).gets('focus').call('textarea_got_focus').on(this);
   3:    when(list).has('changed').call(function() { alert('list_changed'); })
   4:  }

Which also alters dispose to remove the event handler (which is something very tedious to do manually).

So the thing I most dislike in new ASP.NET AJAX syntax is that it is not readable (just plain chaining). I see Event.Behavior as a beautiful solution, jQuery’s as acceptable one (not a language, just more precise naming shortcuts), and ASP.NET AJAX as not really usable.

Same goes to $listen — I just can not remember the correct order of arguments unless looking directly to the documentation or IntelliSense.

But I think that $listen is a great idea, and the solution should be very interesting (considering that IE does not support DOM mutation events).

Templates

Most popular post in my blog is about client-side databinding. I can not show a solution that we have built to solve this issue (we have built it specifically for a project which sources I can not show), so this post is somewhat useless.

I am very hopeful about ASP.NET AJAX’s UI Templates, but I am also thinking about several problems we encountered.  The first one is performance — it is absolutely necessary to pre-cache template binding function. The second one is binding repeated template with server controls.

There is a sample in the roadmap document:

   1:  <!--* for (var i = 0; i < features.length; i++) { *-->
   2:    <span>{{ features[i].name }}</span>
   3:    <!--* 
   4:      $create(Contoso.Tooltip, {
   5:        text: features[i].description
   6:      }, {}, {}, $element);
   7:    *-->
   8:  <!--* } *-->

but I am not sure if it is possible to do this:

   1:  <!--* for (var i = 0; i < features.length; i++) { *-->
   2:    <my:Label Text="{{ features[i].name }}" />
   3:  <!--* } *-->

where my:Label is a ASP.NET AJAX control. It was one the most complex problem for our client:Repeater, so I am interested if this would be implemented.

Now, in contrary to Matt Berseth, I am not really concerned with INotifyPropertyChanged, because it is extremely easy to write a meta-helper to auto-implement it for any given object or prototype in JavaScript.

What I am concerned with with is an idea to “expose methods such as insertRow” for Client DataSource. I do not have any rows in presentational model or my JavaScript arrays, so I strongly dislike this terminology.

The dream feature for me would be a Continuous LINQ for JavaScript, where you can dynamically bind to a dynamically filtered collection, bind to products.where(function(p) { return p.Cost > 5; }). We did a basic implementation for this kind of thing, and found it extremely useful for rich web application. You can have a live model behind a complex page, and never explicitly think of updating any part of the page when some collection in the model got changed.

Animation

I am not really interested in that — other frameworks do this kind of thing easier. And if ASP.NET AJAX is going to imitate jQuery syntax, as some people want, why not just use jQuery or mootools?

Other features

I think that built-in Drag&Drop may make my life easier, looking forward to it. Also, ASP.NET MVC integration has always been a must, it is nice to see it is coming.

All IDE changes are also very welcome.

Summary

In general, I like the proposed changes.

I have a feeling that Microsoft should add more meta helpers as Auto.properties. It is easy to do, but not obvious for the people who are not doing a lot of JavaScript. Also the auto-INotifyPropertyChanged and built-in ObservableCollection would fix databinding cumbersomeness in the same situation.

Also, I am interested in how are the specific technical challenges solved, but it too early to think about that right now.

Sometimes, large company is no better than several independent companies.
I always get this thought when looking at ASP.NET AJAX property accessors.

For people not familiar with the matter:
Microsoft ASP.NET AJAX requires developer to use property accessors to encapsulate javascript fields.
This would be a great idea, if only Microsoft IE supported javascript getters and setters.
Mozilla supports them, and Opera will in 9.50, but IE does not (they are not standard).
Also, IE does not have any hacky way to achieve the same effect (except in VBScript, which seems to be limited).

So in ASP.NET AJAX each property requires two functions named get_propertyName and set_propertyName.

Fortunately, javascript is very powerful in class member manipulation.
So I do not have to write things like this:

MyControl.prototype = {
    get_text : function() {
        return this._text;
    },

    set_text : function(value) {
        this._text = value;
    }
}

And I do not have to wait for auto properties as it is the case for C#.

Instead I just made an helper object named Auto and do things this way:

MyControl.prototype = {…}
Auto.properties(MyControl.prototype, [
    'text',
    'value',
    …
]);

Code for this helper can be very simple.
(in actual project I have additional complexity like Auto support for INotifyPropertyChanged).

var Auto = {
    property : function(prototype, name) {
        var getter = function() { return this['_' + name]; };
        prototype['get_' + name] = prototype['get_' + name] || getter;

        var setter = function(value) { this['_' + name] = value; };
        prototype['set_' + name] = prototype['set_' + name] || setter;
    },

    properties : function(prototype, names) {
        names.forEach(function(name) { 
            Auto.property(prototype, name);
        });
    }
}

This also requires forEach method on Array, but that one is pretty obvious.

I like to show this code when I hear about Javascript being assembly language and whatever-to-javascript compilation.

CSS container class trick

October 8th, 2007

Recently I had a debugging session with one of my colleagues and I remebered a simple trick I use often.
Imagine that you have a list of items, and you want to simultaneously change them in response to a user action.

For example, what if you have this list:

<ul class="Contacts">
  <li>Andrey <span>Shchekin<span></li>
  <li>Nina <span>Philippova<span></li>
  <li>Gordon <span>Freeman<span></li>
</ul>

And you want to show/hide (expand/collapse) all spans in javascript.

One way to do this would be to go through all spans and change their className.
But that can be quite slow on large list.

The better way is to use something like addClassName (from prototype.js) on <ul>.

So you change it to <ul class="Contacts AllCollapsed"> and then apply styles to .AllCollapsed li span.

This way the browser is responsible for finding all contained elements, which should be faster.
Also, if elements are added dynamically, you do not have to process them.

Evaluating Javascript in WatiN

September 5th, 2007

The WatiN framework is quite cool, but it lacks two important things.
First one is searching by CSS selectors, or, at least, classes.
Find.ByCustom(“className”, “X”) is way too ugly. Or am I missing something?

The second (more important) one is a weak access to Javascript.
First thing I wanted to do with WatiN was to change something and then check some script state.
And getting some values from script was not obvious.

I didn’t want to use Ayende’s evil hack (no harm intentended, it gets the work done) — putting javascript state into DOM is not pretty and too string oriented.
I thought that browser COM interfaces should definitely have a way to get Javascript objects outside, that is just the way MS/COM people think.
Thanks to Jeff Brown’s comment for explaining last obstacles.

So here goes the code.
It is quite basic, but it allows you to get value of any Javascript evaluation.
As you can see, I hadn’t included any error handling, I had no time to look into it.

    public static class JS {
        public static object Eval(Document document, string code) {
            IExpando window = JS.GetWindow(document);
            PropertyInfo property = JS.GetOrCreateProperty(window, "__lastEvalResult");

            document.RunScript("window.__lastEvalResult = " + code + ";");

            return property.GetValue(window, null);
        }

        private static PropertyInfo GetOrCreateProperty(IExpando expando, string name) {
            PropertyInfo property = expando.GetProperty(name, BindingFlags.Instance);
            if (property == null)
                property = expando.AddProperty(name);

            return property;
        }

        private static IExpando GetWindow(Document document) {
            return document.HtmlDocument.parentWindow as IExpando;
        }
    }

Nitpicking:
By the way, Ayende, getting permalinks to comments in your blog is not obvious (I used View Source).

Recently I got an optimization problem in ASP.Net.
To be short, I had a Repeater with custom (somewhat complex) template on my Page, and I wanted to reload it asynchronously.

The first solution was XP and didin’t consider performance at all: wrap Repeater inside an UpdatePanel.
The problem was that the entire Page had to be repopulated on server just to get to the Repeater.

That gave me a choice of two headaches:

  1. Put all Page/Controls data into ViewState and bloat bandwidth.
  2. Query all additional data on the reload request and increase load on database to get data that will be thrown away.

To be honest, I could solve (2) with server-side cache, but, in my opinion, caching does not make ugly solutions any better, just faster.

So, naturally, my thought was to query the data-only WebService and then populate the Repeater on client.

And it was interesting to find out that Microsoft already has a client-side data binding solution within ASP.Net AJAX Futures.
I have found an excellent article on this matter by Xianzhong Zhu, “Unveil the Data Binding Architecture inside Microsoft ASP.NET Ajax 1.0″ (Part 1, Part 2).

I will now give a quick summary on the overall client-side binding architecture.
In essence it is quite similar to the smart DataSource controls of ASP.Net 2.0:
There is a DataSource javascript component and a ListView javascript control with html template.
ListView passes data from/to DataSource control, and DataSource talks with a JSON Web Service as a backend.
Controls and their relations are described in text/xml-script (Futures-only feature).

Everything seems quite straightforward and easy to use, I was quite happy to find it.
One thing that bothers me is the performance of text/xml-script (it is parsed on client).
But it is a concern not related to the current story.
The other question is what to do when I want to databind a complex list (consisting of several embedded server user controls) ?
I am going to find it out real soon.

Along the way, I have also noticed Sys.Preview.Data also introduces DataSets/DataTables to javascript.
That is quite funny. Personally, I never really considered DataSets acceptable anywhere above Persistence layer.
But I already thought about Persistence/DataAccess concept in javascript when I saw Gears.
And DataSets seem to fit ‘nicely’ to some GoogleGearsDataSource (it would be quite an experience to actually see one in real code).

Well, javascript O/R Mapper, anyone ?

Since my previous post on microformats, I have decided that my opinion in this matter needs more evidence.
While I could collect all following information before writing the post, I didn’t have enough motivation to do the research.
But now, after writing it, I have my self-esteem as a motivation.

Ok, so I proposed using (namespaced) custom tags instead of overloading existing ones.
Now let’s go scientific and see what questions this solution may rise.

  1. Do modern browsers support CSS styling for unknown tags in HTML documents?
  2. Can these tags be added to document without breaking standard compliance (validity)?
  3. What possible problems can arise from using non-standard tags in modern browsers?

For practical purposes, these can be converted into two main questions

  1. Should custom tags work?
  2. Do custom tags work in modern browsers?

And the answers are:

  1. By default, no.
  2. Not perfectly, but yes.

Now let’s discuss it in detail.

To understand the first answer is to understand what exactly is HTML, what is XML and what is XHTML.
The most important (maybe obvious) point is: HTML is not a subset of XML and HTML is not compatible with XML.
HTML and XML are both a subsets of SGML, and SGML does not provide a way to mix different subsets within a single document.
So custom XML tags are not allowed in a HTML document.

While there are some solutions that allow arbitrary XML to be placed in a HTML document.
For example, Microsoft has XML Data Islands.
But they can be considered grammar hacks due to XML-HTML incompatibility.

Practically, however, HTML documents have to be viewed as “tag soup” by the browsers, so custom tags do not cause document rendering to fail.

So, if I am formally out of luck with HTML, what about XHTML?
For simplicity, one can view XHTML is a rewrite of HTML to follow XML rules.
So any custom tags should be allowed in XHTML if they are properly namespaced.

But there are a lot of problems with authoring XHTML.
While some of them are more like challenges (script/style syntax), one is extremely important.
The only way to tell modern browsers that that the document is XHTML is to serve it as application/xhtml+xml
(See this document for an excellent explanation).
And Internet Explorer doesn’t support XHTML at all — so it refuses to render application/xhtml+xml.
(It doesn’t mean IE can’t open XHTML. When XHTML document is sent as text/html, IE renders it with HTML engine).
So I was out of luck once again.

At that point I understood the reasoning of microformats.
Standard compliance is an important part of better Web, and there is no completely valid way to use custom tags.

But what is with the second question? It seems that actual situation is way better than one could suppose.
Firefox, IE7 and Opera 9 all could render the custom tags style correctly in the document served as text/html.
(To be really pedantic, I set DTD and xmlns to XHTML.
After all, even if text/html documents are never parsed as XHTML, MIME Type is a server setting, not document one.)
But IE7 has a one important characteristic — it does not render custom tag styles unless there is an xmlns for their namespace on html tag.
No other tag is sufficient.

What does it mean? It means that while one can make a document that is styled correctly in these IE7,
document part containing custom tags can not be reused without providing a namespace on the aggregating document.
But it not an extremely important point, since for aggreagation one does not actually control styles as well.

So, practically speaking, one can create a document that uses custom XML tags for the cost of formal document validity.
(The document can still be made formally valid by using custom DTD, but this will put IE and FF into quirks mode).

By the way, the challenge of adding custom tags to HTML was faced by MathML (mathematical markup language) community for years.
If you are interested, you can read these discussions:

Personally, I still see microformats as a step in wrong direction.
While hCard provides HTML with a way to express the vCard semantics, I would prefer it to be just a HTML-compatible way, not the recommended one.
I see HTML as standard that needs support, but not popularized extensions.

I really like what is happening to Web.

Cool-new-ajaxy sites are often actually more friendly, useful and powerful.
Web development seem to become way less hacky.
And a lot of standards that are gaining adoption are actually extremely useful (think about RSS).

But there is a group of new standards that I fail to understand.
They are called microformats.

In my understanding, there are three pillars of Ideal Web:

  1. Markup provides semantics
  2. Styles provide presentation
  3. Scripts provide behavior

These blocks are logical, understandable, maintanable and loosely coupled.
It is worth noting that all strict DTDs are here to make the markup truly semantic and help achieve such separation.
This is why I write <strong> instead of <b>.
And this is what helps Web 2.0 applications to be really rich without being messy.

And for me, microformats are viral semantics.
They infect markup and overload it with additional meaning, turning it into an ill, bloated mess.
The microformats wiki states:

Reuse the schema (names, objects, properties, values, types, hierarchies, constraints) as much as possible from pre-existing, established, well-supported standards by reference

For me it seems more honest to say overuse, since the most interesting thing about microformats is that there are no actual problems they solve.
Consider this fragment:

<span class="tel"><span class="type">Home</span> (<span class="type">pref</span>erred):
  <span class="value">+1.415.555.1212</span>
</span>

I would prefer:

<tel><type>Home</type>(<type>pref</type>erred):
   <value>+1.415.555.1212</value>
</tel>

Now it does not seem that somebody is reusing iron to hammer nails.

It is 2007. XML is here and it is supported. X in XHTML stands for extensible.
IE did not support CSS namespaces, but you could write styles like vcard\:tel for years.
And this syntax does not seem like a show stopper to me.

Actually, upon reading on topic, I immediatelly googled for “microformats are stupid”.
The first thing I found was Why I Hate Microformats? by Robert Cooper.
He points to the same things I do, but he misses the fact that we had no need to wait for the IE7.

There is also a more interesting post Must Ignore vs. Microformats by Elliotte Rusty Harold.
The one point I do not agree is that Elliotte argues that XML does not have to be valid.
I do not see why the properly namespaced XML in XHTML would not be valid, but I will have to test it myself.

Web would be better if microformat authors read more about XHTML and did some browser tests before pushing this standard.