Friday, 20 June 2008

Well, I wrote about one way to do deeplinking and knew that there had to be something out there that already did this.

Look no further. It’s here!

Friday, 20 June 2008 23:11:52 (Romance Standard Time, UTC+01:00)  #    Comments [8]  |  Trackback
 Wednesday, 18 June 2008

Ninject is a lightweight dependency injection framework and it has been getting quite a bit of attention lately.
What makes is superspecial, is that it runs under Silverlight 2.0 beta 2!

The Ninject website is here and Nate Kohari talks about this release here. From his post:

So, what are some of the features of Ninject 1.0?

  • Constructor, property, method, and field injection
  • Instantiation behaviors (singleton, one-per-thread, one-per-request)
  • Fluent interface for declaring type bindings
  • Contextual bindings, where the selection of which type to instantiate can be delayed until activation
  • Support for instance scope and deterministic disposal
  • Fully pluggable, modular design: each kernel component can be easily replaced to alter the framework’s behavior
  • Lightweight interceptor support (aspect-oriented programming)
  • Integrations with other popular frameworks

It’s great to see people working on MVC approaches and now even DI frameworks for SL. Keep it coming!

Wednesday, 18 June 2008 11:42:42 (Romance Standard Time, UTC+01:00)  #    Comments [6]  |  Trackback

Nihkil wrote sometime ago about ‘actions’, which was a concept he created that attach some behavior to elements. Think of the action of pressing the ‘enter’ key in a textbutton and executing some logic (sparing the user a click on the button next to the textbutton).

He has clearly been thinking more about his framework and now posts about the MVC concept of the ViewModel, extending it with his actions here. Good write-up. Go read it.

Basically, he explains what a ViewModel is and shows how to execute ‘command’-like behavior on them. As you might know, Silverlight does not support the concepts of commands, like WPF does. His syntax is like this:


  1 <vm:View xmlns="..." xmlns:x="..."
  2   xmlns:vm="clr-namespace:Silverlight.FX.ViewModel;assembly=Silverlight.FX"
  3   xmlns:app="clr-namespace:AmazonSearch.Views">
  4   <vm:View.Model>
  5     <app:SearchViewModel />
  6   </vm:View.Model>
  8   <Grid>
  9     <TextBox x:Name="searchTextBox" />
 10     <Button Content="Search" IsEnabled="{Binding CanSearch}">
 11       <vm:ButtonEvents.Click>
 12         <vm:InvokeMethod MethodName="Search">
 13           <vm:ElementParameter ElementName="searchTextBox" ElementProperty="Text" />
 14         </vm:InvokeMethod>
 15       </vm:ButtonEvents.Click>
 16     </Button>
 18     <ItemsControl ItemsSource="{Binding Products}">
 19       <ItemsControl.ItemTemplate> 
 20         <DataTemplate><app:ProductView /></DataTemplate>
 21       </ItemsControl.ItemTemplate>
 22     </ItemsControl>
 23   </Grid>
 24 </vm:View>

The thing to note is in lines 10 to 15. There he invokes a method straight on the ViewModel.

The concept is quite the same as the Caliburn project from Rob and the idea is very powerful!
It enables you to have no code-behind and go straight to the viewmodel. Very nice!

Thinking about this a bit though, does make me wonder if the added Xaml is worth the ability to go straight to the viewmodel. Wouldn't it be just as simple to define a Search method on the codebehind and invoke the correct method in the viewmodel?

My point being: is it worth to incorporate such a framework (albeit very small and succinct). What do you think?

Wednesday, 18 June 2008 10:04:08 (Romance Standard Time, UTC+01:00)  #    Comments [8]  |  Trackback
 Friday, 13 June 2008

I’ve been busy sharpening my Silverlight skills and created my very own button, complete with VSM.

The button (‘rjButton’) inherits from contentControl and in the project there is a generic.xaml which defines a default look for the button, including VSM definitions and state transitions.
When loading up my solution in Blend, I can happily get the rjButton in my page. It looks correct. However, when I ‘Edit a copy’ of the template, nothing shows up!! Funnily enough, when I use ‘Create empty’, the correct states do show up.

I was unable to google-fix the problem. I would guess that when you use ‘create empty’, Blend just looks at the attributes on your class and shows the correct states. When you ‘Edit a copy’, Blend looks for the template and can not find any. Somehow it is unaware of the link to the style in generic.xaml, and it creates an empty style.

I’ve double checked the behavior with the TabControl, which is also a control that is defined in an external control, and it works the same.
I'm not sure why controls included in the framework do work correctly. I've taken a look with reflector and I've seen nothing out of the ordinary.

You can work around this by naming the style and explicitly tell the control to use the style. But then again, it might be easier to just copy the style (use David's excellent style browser here).

If you know what is going on, leave a comment!

[update: jasonxz knows: I was informed, today, that Blend does not, yet, support the "edit a copy" functionality of a Template that is not defined in System.Windows.dll. Thnx! ]

Friday, 13 June 2008 17:45:21 (Romance Standard Time, UTC+01:00)  #    Comments [4]  |  Trackback

I just spent way too much time figuring out why my VisualStateManager suddenly started giving errors. Without ‘break on all exceptions’ I got a ‘Catastrophic error’. With breaking on all exceptions I could finally see that the layout system was trying to layout the visualstatemanager.

I basically had specified my vsm directly under the controltemplate, instead of defining it inside the grid. Whoops!

Friday, 13 June 2008 15:01:00 (Romance Standard Time, UTC+01:00)  #    Comments [5]  |  Trackback
 Wednesday, 11 June 2008

I was triggered to spend some time on thinking about deeplinking, when I was listening to a podcast with Neal Ford, here.
In it, he has quite a few arguments why something like Silverlight (and Flex for that matter) will never amount to anything. I disagree with almost all of his points, but one stuck with me more: the inability to do deeplinking.

Let me start off by saying that I think the ‘normal’ html world has reached maturity and should soon begin to disappear. As almost everything in the world, technology adoption follows a wave pattern. Html has had some great advantages which made it easy to adopt. However, as computing power increases and humans become more accustomed to great applications, html as a platform does not deliver anymore. It was rejuvenated by the Ajax revolution, but in the end, you are always fighting against the restrictions that it imposes.

Those restrictions are no longer necessary. Flash did not deliver as a RIA platform, but Flex seems very capable, as does Silverlight. It will take a few years, but the demand for rich clients will drive the adoption of said technologies.

Being able to do deeplinking, is an important part of the experience and usability. The more I thought about it, the more I agreed on this. Although I think that browsers (as we know them) will cease to exist pretty soon or more likely: change to meet new needs, for the next few years we will have to deal with the restrictions they impose.
So, I started to think about how we can solve the deeplinking issue for Silverlight.

I had a flash of brilliance when I thought of the achor (#) sign in url’s. They can be navigated to, but the page is not reloaded. Exactly what was needed for deeplinking.
After doing some fast research, I discovered half the world had already thought of this trick and it is heavily used by the Flex world.
That discovery ruined my chances to score some ‘smart'-points with my girlfriend, but it won't keep me from implementing my idea ;-)

The basic idea

The idea is to get to the url at the beginning of the application and treat everything after the # sign as 'state'. This state is used by the components in our application to initialize themselves to the correct state. For instance, show the help page, or the products page.
When a component is changed and it is important enough to reflect this change in the url, we use javascript to navigate to the new url. The browser will recognize that only the anchor has changed, and will not really browse there. However, the user can now confidently copy the url.

It's pretty easy.

Two approaches

Using a navigationcontroller.
Your application could instantiate one navigationcontroller. This controller would be used inside your application to show different usercontrols etcetera. I think such an approach is well suited for a MVC-style of application architecture.
Obviously, since all your navigation is taken care of by a central component, it would be very easy to take care of 'serializing' its state to the url.

Using per component approach.
If you're just not that kind of person, you could also just make the components you care about do the (de)serializing. So, possibly react to the Loaded event of a component and reading the url to see how to initialize it.
I've taken this a step further and created a class that serializes the vertical offset of a Scrollviewer. It can be used like so:

  1         <ScrollViewer x:Name="sv1" VerticalScrollBarVisibility="Auto" Margin="10">
  2             <nav:ScrollviewerOffsetStateAttacher.Register>
  3                 <nav:ScrollviewerOffsetState TemplateName="HelpTemplate" PartName="pos1" />
  4             </nav:ScrollviewerOffsetStateAttacher.Register>
  5         <TextBlock TextWrapping="Wrap">   
6 Lorem ipsum dolor sit amet, conse

(pretty radical, isn't it. Here I'm serializing the amount of scrolled pixels to the url. That's something else than just which page you are viewing!)

Some more code

First off, you need to think about how the url is serialized. Some kind of template needs to be known to the system. And, different templates should be available for different parts of your application. So, during initialization of my application I do this:

            NavigationState.RegisterTemplate("MainNavigationTemplate", "mainpage");
            NavigationState.RegisterTemplate("ProductTemplate", "mainpage/product/detailpos");
            NavigationState.RegisterTemplate("HelpTemplate", "mainpage/pos1/pos2");

A better approach might be to supply regex expressions.

As you have figured out by now, I'm using a static class 'NavigationState' to manage my url fiddling. It contains a SetNamedPartState and a GetNamedPartState method. So when I navigate to the Products page, I might do this:

NavigationState.SetNamedPartState("mainpage", "ProductTemplate", "products");

I'm telling it to use the producttemplate and set the mainpage part of that template to the state 'products'.
During the load though, I do the opposite:

string state = NavigationState.GetNamedPartState("mainpage", "MainNavigationTemplate");
if (!String.IsNullOrEmpty(state))
    if (state == "products")
    else if (state == "help")

Getting the url is easy:
string uri = HtmlPage.Document.DocumentUri.ToString();

Setting it is only slightly harder:
    NavigationApplicationString, InternalStateString));

Conclusion, work ahead

It's pretty a pretty simple idea. I like the way I attached a 'state' object to a scrollviewer control to make a no-code, designer friendly experience possible.

If someone would get serious about this, I guess they would take a look at the mvc approach. They also hook the url's you are setting, to the back button(!) So, there should be good crossbrowser javascript available.

Also, a good and flexible url parsing engine is necessary.

Finally, when you take the approach of one controller doing all the hard work, nothing much has to be done. However, I can see the creation of all kinds of specific classes that can be attached to controls to make them 'url-persistable' (think of selecting the right listbox item).

Try it out

The homepage of our sample application:

Two url's with state in them:

I will not keep this application available forever and probably not update it to the release version of beta2.


Who is going to make themselves useful by creating a robust solution? Leave a comment of mail me if you want the source code!

Wednesday, 11 June 2008 20:48:01 (Romance Standard Time, UTC+01:00)  #    Comments [85]  |  Trackback
 Thursday, 05 June 2008

Okay, I've been busy with other stuff in my life, I'll blog about soon. Suffice it to say, I'm going to be able to focus my time more on Silverlight now ;-)

The Silverlight team is announcing beta 2 with this post. It's a pretty long list with changes, and it's looking very good! Here are a few of my favorites:

  • They included some controls into the runtime. So more goodies without added download size.
  • A visual tree helper. I'm looking for more information on this. As you know, SL does not have the same concept of a seperate visual tree and logical tree as WPF does. They instead opted to not differentiate. Does this helper mean that the two models come closer to each other?
  • Per binding level validation.
  • Binding to attached properties! Yay!
  • OnItemsChanged method
  • Fallback value during conversion
  • Duplex communication. Oh dear, they really hit the sweet spot here. This allows you to push data to the client during a call.

The big one for me is support for UIAutomation though. I'm not sure if it is supported fully, but this means you can test your controls with actual 'human'-like input. I think this is important when building an application with a late-bound system like Xaml-binding.

The whole blogosphere is raving about the new VisualStateManager. It is a highlevel api to work with your states. The blend team is able to give you a much improved templating story because of it. Read about it here or here.

Thursday, 05 June 2008 11:14:48 (Romance Standard Time, UTC+01:00)  #    Comments [2]  |  Trackback