Convention based page and view-model discovery

By default the Okra App Framework uses attributes to annotate the pages and view-models for discovery (see here for more information). Often however there will be a common naming pattern throughout the application. In a convention based approach you no longer need to apply attributes to classes. Instead they are automatically discovered based on this common naming system. For example, all pages may be named XxxPage and view-models named XxxViewModel, where “Xxx” is the associated page name.

Setting up convention based discovery

The Okra App Framework supports convention based discovery by configuration of the underlying MEF composition container in your application bootstrapper. For example to apply the above conventions you would simply override the GetContainerConfiguration() method as follows,

public class AppBootstrapper : OkraBootstrapper
{
    ...

    // *** Overriden base methods ***

    protected override ContainerConfiguration GetContainerConfiguration()
    {
        ConventionBuilder conventionBuilder = new ConventionBuilder();

        conventionBuilder.ForTypesMatching(type => type.FullName.EndsWith("Page"))
                         .Export(builder => builder.AsContractType<object>()
                                                   .AsContractName("OkraPage")
                                                   .AddMetadata("PageName", type => type.Name.Substring(0, type.Name.Length - 4)));

        conventionBuilder.ForTypesMatching(type => type.FullName.EndsWith("ViewModel"))
                         .Export(builder => builder.AsContractType<object>()
                                                   .AsContractName("OkraViewModel")
                                                   .AddMetadata("PageName", type => type.Name.Substring(0, type.Name.Length - 9)));

        return GetOkraContainerConfiguration()
                .WithAssembly(typeof(AppBootstrapper).GetTypeInfo().Assembly, conventionBuilder);
    }
}

Note the use of lambda expressions to identify all types ending in the words “Page” or “ViewModel”, and the Substring expression to extract the page name from the type name. Also note that the convention based configuration must be appended to the result from a call to the GetOkraContainerConfiguration() method so that the core Okra services are included.

Using convention based discovery

Once convention based discovery has been configured you can now simply define pages and view-models following the convention.

For example to define a page named “Foo”,

public sealed partial class FooPage : Page
{
    ...
}

public class FooViewModel
{
    ...
}