Tuesday, October 22, 2013

Catel extends Prism modularity options through NuGet


Prism provides a lot of options regarding modularity by default. Fact is that most of the stuff  you need to build a modularized application is available on Prism. Prism contains several modularity options including ways to retrieve modules from a directory, set them up through the configuration file, and even options to create modularized Silverlight applications.

On the other hand, Catel provides support for module catalog composition in order to enable more than one modularity options into a single application.

Nowadays, initiatives around NuGet come from everywhere, such as Shimmer with the same goal of ClickOnce (but works), OctopusDeploy for release promotion and application deployment or even the recently released extension manager of ReSharper 8.0.

So, the Catel team comes with a new one and the fact is that we wondered why no one told about this before: 

What if you would be able to distribute your application's modules through NuGet?

If you want to know how, take a look.

Enabling NuGet based modularity option

With the forthcoming 3.8 version of Catel you will be able to install and load modules from a NuGet repository. The only thing you have to do is:
  1. Write a module as you know with Prism (or better in combination with Catel).
  2. Create a NuGet package for the module and publish it into your favorite gallery.
  3. Use and configure the NuGetBasedModuleCatalog in the application’s bootstrapper.
The first two steps are well documented. For details see creating and publishing a package and declaring modules from NuGet and Catel documentation.

So, now we can focus on the third one.

Use and configure the NuGetBasedModuleCatalog in the application’s bootstrapper

In order to simplify the following explanation we published a package into the official NuGet Gallery named Catel.Examples.WPF.Prism.Modules.NuGetBasedModuleA. Such package contains an assembly with a single class like this one:
public class NuGetBasedModuleA : ModuleBase
    public NuGetBasedModuleA(IServiceLocator container):base("NuGetBasedModuleA", null, container)

    protected virtual void OnInitialized()
      var messageService = this.Container.ResolveType<IMessageService>();
      messageService.Show("NuGetBasedModuleA Loaded!!");

Let’s start writing an  application that will use this public packaged module. Indeed, the main point of interest here is about the usage and configuration of the NuGetBasedModuleCatalog. Therefore just write the bootstrapper as follow:

public class Boot : BootstrapperBase<MainWindow, NuGetBaseModuleCatalog>
  protected override void ConfigureModuleCatalog()
    this.ModuleCatalog.AddModule(new ModuleInfo 
               ModuleName = "NuGetBasedModuleA", 
               ModuleType = "Catel.Examples.WPF.Prism.Modules.NuGetBasedModuleA.NuGetBasedModuleA, Catel.Examples.WPF.Prism.Modules.NuGetBasedModuleA", 
               Ref = "Catel.Examples.WPF.Prism.Modules.NuGetBasedModuleA, 1.0.0-BETA", 
               InitializationMode = InitializationMode.OnDemand

Notice how the Ref property of ModuleInfo is used to specify the package id and optionally the version number. If the version number is not specified then the application always will try to download the latest version keeping the modules up to date.

Finally, to make this demo work, just put in the XAML of the main window the ModuleManagerView control, run

and click the check box.


Yes, we did it again. Catel keeps working alongside Prism. Now, we extended Prism’s modularity options through NuGet in order to provide a powerful mechanism of application module distribution. 

If you want to try, just get the latest beta package of Catel.Extensions.Prism and discover by yourself all scenarios that you can handle with this Catel exclusive feature.


  1. When is the Catel 3.8 going to be released?

    1. Take a look into the road map https://catelproject.atlassian.net/secure/Dashboard.jspa

  2. Does this mean, it can automatically load all the nupkg modules from a directory?

    1. Indeed you can do it but in order to load common “modules” from a directory the best options are DirectoryModuleCatalog or SafeDirectoryModuleCatalog (from Catel).

      If you set the PackageSource property of a NuGetBasedModuleCatalog instance to a local or remote local folder path, then you are able to load the selected “packaged modules” (.nupkg files with modules) from such directory.

      The default value of the PackageSource property is https://nuget.org/api/v2/, so the modules in the example are loaded from the official NuGet repository.

  3. You can find updated documentation including also new features here