It works in my computer (Starting problems – Jounce)

I was out on a vaccation and happy to be back. I will post couple of pictures later.

Now to the fun part, Couple of my friends have a problem developing ‘Hello World’ program using Jounce. Now that Jounce 1.0 is out, it is no longer required to download the source code to build and generate the dll to use. You can now download the single Jounce.dll directly from download page or using NuGet get the Jounce Package. So my friends tried the first approach by using the single Jounce.dll. The program compiles just fine but when you run the program, it fails at runtime. But I could create ‘Hello World’ program all day and it does not fail at run time. By the way, I followed the same steps by friends did. As all the programmers say, ‘It works on my PC’ 🙂

I always like good debugging. So I sat with one of my friend and see what is happening. For starters, when you create Jounce application, you end up deleting all the code from App.XAML.cs since application startup will be taken over by Jounce Framework. Since there are no code in App.XAML.cs, the trapping error was little difficult. So I went in and put the code the catch the unhandled exception in App.XAML.cs. With that armed, put a break point inside the unhandled exception code, when I looked at the error log, I could see, it is looking for ‘System.Windows.Interactivity.dll’ and that was not in the reference folder. We added the missing dll and there it is, ‘Hello World’.

Now the question, how come it worked in my box not on my friends, we both did the same things. The only difference was, I have Expression Blend installed and this dll is available in GAC to find it. So the bottom line, is if you are using Jounce and do not have Expression Blend installed, make sure you have this dll in your reference other wise you will run into the same problem. You will need this dll if you are going to use MVVMLite or Caliburn.Micro as well.

There is still an outstanding issue with NuGet, with out Expression Blend install, Nuget install for Jounce is failing. I haven’t got ten around to see why is it failing. I will update this post once I get an answer.

** Update – “I looks like maybe one of the Expression SDK because of the Navigation Trigger. Will see if I can add the dep to pkg” from our good friend Jeremy. **

Hope this helps someone.

Expression Blend Tutorial link

Lately I have been working on design time data and unit testing with respect to MVVM frameworks. Most of the design time data work I have done is in the XAML with interfaces. That brings up another question, does these frameworks ‘blendable’? Unfortunatly I never did any work on Expression Blend, so I switched my focus to Expression Blend for the last two days with design time data in mind. This morning I came across the following link and it is worth sharing and useful any expression blend newbies like me. If you all have any MUST read for expression blend newbies, please send it to me.

XAP Optimization – Part II Versioning

So we are all not just building one simple Silverlight project and publishing simple web pages. Most of us develop enterprise LOB application in Silverlight. When you develop that big application you will end up using same component again and again over multiple projects and also you will end up using multiple version of same controls over multiple places as you develop. When you develop major application, if you get a new version of a third party control or even your own control, you will not replace it everywhere because of the regression testing. You will end up versioning and upgrade the solution with version.

In my previous blog on XAP Optimization, I looked at the simple attempt to reduce the size of a small Silverlight application. We looked at two different approaches. From 880Kb, we were able to get it down to ~230KB. I looked at the XAP file to see what is taking that much space and it turned out, I am using Component One controls for UI and Jounce for MVVM Framework. My dll by itself, unzipped only 14k. I was ok with the size of the file since, some of my application would use one version of Component One control and some other XAP files would use different version of the Component One control so If I would strip them out and make it common zip file then I would run into version conflict. So I was happy with the result till last weekend 🙂

It turned out, even though we use different version of controls, as we make changes we bring the projects to latest controls, so 80% of them require version of the controls. So it makes sense to even strip the controls out of XAP to reduce the file size and also reduce repeated loading of common controls, but somehow put versioning in place.

So by default, System controls become ZIP file when we use XAP optimization and how would be able to do the same for other controls and our own libraries? The answer is very simple. If you would open up the XAP file, you would see


The first file is AppManifest.xaml,

<Deployment xmlns="" xmlns:x="" EntryPointAssembly="XAPOptimization1" EntryPointType="XAPOptimization1.App" RuntimeVersion="4.0.50826.0">
    <AssemblyPart x:Name="XAPOptimization1" Source="XAPOptimization1.dll" />
    <AssemblyPart x:Name="C1.Silverlight.FlexGridExcel" Source="C1.Silverlight.FlexGridExcel.dll" />
    <AssemblyPart x:Name="Jounce" Source="Jounce.dll" />
    <AssemblyPart x:Name="System.Windows.Interactivity" Source="System.Windows.Interactivity.dll" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />
    <ExtensionPart Source="" />

If you see there are two parts of Deployments. One is Deployment.Parts which specifies all the dlls that are in the XAP file and associated name space. The second part specifies all the zip files that might be required for application to run. In my opinion the only thing that should be in XAP file will be the application dll. So the two part question is how would you get all the common dlls separated into its own ZIP file and how did you update the Application Manifest to reflect it?

Here is a very good article explaining how to Configure an assembly for use with application library caching. Please read this link since it goes more detail about the Application Manifest file and also ext map XML file.

Any dll that is common and it need to be in a separate Zip file, should have associated ‘extmap’ file. What it means is, in the above project you see that I am using System.Xml.Linq.dll, if you would find the file location using the file property and navigate to the file location, you will see following files, The file we are interested in is the dll file name with ‘extmap.xml’

imageIf you would crack open the System.Xml.Linq.extmap.xml, you will see the following

<?xml version="1.0"?>
<manifest xmlns:xsi="" xmlns:xsd="">
    <extension downloadUri="" />

The first two line is name and version and the third line is the public key of the dll, that means anything you want to have as separate dll, have to be strong named. Next two specifies the relative path of the dll and where do you get it from. In our case, the dll is in a zip file in the same path of the XAP file.

Have a look at this blog, here the author explains how it is done and also provides a tool to create your own extmap files for your dlls.

Once we have extmap files created for the dlls that need to be separated and placed on the same path where the dll located, when compiled with XAP optimization enabled, all the ones with extmap files will be in separate ZIP files.

Now comes the question of versioning, some XAP files would use different version of same controls, so by creating extmap file we would end up overwriting the old one with new one and potentially crashing the  application. How do we solve it, again it is very simple, now most of all third party controls comes with extmap files, including Component One. Whenever we get latest version of a control or our own library, I run a small ruby script, which run through all extmap files and adds version number to the destination zip file. So instead of

<ExtensionPart Source="" />

our implementation would look like the following

<ExtensionPart Source="" />

That’s about it. So when I compile my project pointing to the new version dll, it uses the modified extmap and generate version numbered zip file thus making all the project work without any problem. I am working on a script which will then walk though all the XAP files and look at the Application Manifest and remove any unwanted zip files from the deliver location thus keeping the folder clean.

Once I have the second script done, I will post both the scripts in the blog here.

To test this, I created two Silverlight applications. Both are exactly same except the first one uses version 152 of Component One dlls and second one uses version 183. Now if I would run, each application should use appropriate ZIP and run without any problem. So I ran the fiddler and then ran the application to see the what is it downloading and is it caching.


First I ran XAPOptimization with version 152 and as you can see the first green box shows all the files that got downloaded to the client. Now when I tried the second version of the XAP Optimization with version 183, as you can see it did get the version 183 and also it skipped the common files that was already downloaded by the first version. For example. was not downloaded since it was downloaded along with the first XAP file.

I see lot of potential in using XAP optimization when developing large application. Hope this helps someone.

One thing I forgot to mention, with versioning and keeping couple dlls in the XAP file itself, we are at ~100kb. That is a excellent saving. So next time when we make a change the the solution and none of te thrid party control changes, our download is only the XAP file size that is ~100kb not 880kb.

MVVM Frameworks Compare and Contrast – 1

This subject will never be accurate, regardless I am going to take a stab at it. The question is, if it is not going to accurate why do it? Well, first to educate myself with all available framework. I am sure by looking at different framework, learn some neat stuff on coding and patterns. One last thing, by putting it out in it blog if I am wrong, I will know and correct myself. One last point, some of the items become out-of-date soon so I will be very clear on which version and build I am using as I do this blog.

Before I go any further, I would love to hear from you, which framework are you using and if you could explain why you choose that will help me a lot.

Couple of things I need to tell upfront;

  1. This is purely for Silverlight, sorry no WPF or WP7.
  2. I have been using Jounce for a while and I love it. So I might have bias towards Jounce so if you see it please correct me.
  3. I might not cover all the features in all the frame works, so if you think I might have missed something, please let me know.

Now for the MVVM Framework comparison, I am going to use the follow common frameworks available.

I am thinking of covering following subject on each of the frameworks. If you can think of some feature I need to add here, please let me know as well.

  • Documentation and samples.
  • Simple Hello World
  • Event Aggregation
  • Commanding
  • Region Management
  • Navigation
  • Working with Multiple XAP files.
  • Design Time data and Blentability.
  • and more

Why my Commands did not work in Jounce

If you haven’t used commands in Silverlight, you have to try it. It is another beautiful way to move code from code behind to view model. If want to know how to use Commands, have a look at Jounce Codeplex or have a look at my blog.

Now lets go the problem I faced.  In XAML the Command and CommandParameter was defined properly. In the ViewModel both the commands are declared public and are initialized in the ViewModel constructor. Also both the execute methods are are declared and defined properly.  Now I was told, no compilation error and when you run, the command method never hits. After 30 minutes of debugging (I know it took some time, when you are not looking for the obvious), I found out that the command declarations were missing the getter and setter. Right after adding the getter and setter, it worked like a charm. So it is important to note that, if you are exposing something from ViewModel to view, make sure Jounce can get to it by declaring it as property.

Just in case you run into any problems, here are the things you need to watch out for using Commands

1. Make sure Command and CommandParameters are defined in the XAML and they bound to appropriate fields in ViewModel.

2. Make sure the command variables are declared ‘public’ and have getters and private setter.  ‘{ get; private set; }’

3. In the ViewModel constructor, you instantiate the command with execute method.

ButtonCommand = new ActionCommand<string>(CommandMethodToExecute)

4. Make sure the method signature correct. (In this case, if it is wrong, it will give compilation error).