Uno Platform ViewModelLocator

Question

I'm testing uno platform solution to see if it's flexible enough and can integrate pre existing autofac (6.2.0) and Autofac.Extras.CommonServiceLocator(6.0.1) stuff in it. I want to add the ViewModelLocator to auto resolve view models. it's working with UWP and wpf project, but not with droid or WASM. I added in shared app.xaml the resource

<Application
     <Application.Resources>
      <ResourceDictionary>
         <ResourceDictionary.MergedDictionaries>
            <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />

            <!--  #Region MVM light view model locator  -->
            <ResourceDictionary>
               <local:ViewModelLocator x:Key="ViewModelLocator" d:IsDataSource="True" />
            </ResourceDictionary>
            <!--  #Endregion  -->

         </ResourceDictionary.MergedDictionaries>
      </ResourceDictionary>
   </Application.Resources>
</Application>

In the mainpage.xaml

   DataContext="{Binding [TestViewModel], Source={StaticResource ViewModelLocator}}"

whit this configuration the constructor is called at startup where I also want to set up Inversion of control stuff

        public ViewModelLocator()
        {
            this._container = IOCContainerConfig.Configure();
            var serviceLocator = new AutofacServiceLocator(this._container);
            ServiceLocator.SetLocatorProvider(() => serviceLocator);
            //this._dbContext = serviceLocator.GetInstance<IContext>();
            //TestDbConnection(this._dbContext);
        }

As said this is not working with other kind of projects like droid or wasm the constructor of the locator is never called but I don-t have errors, just page is loaded without the viewmodel behind.

Any ideas or tips to make it working for all projects?

Answer 1

Depending on the type of resource, Uno Platform is initializing some resources in a ResourceDictionary lazily only when they are accessed. This is done as a performance optimization.

To guarantee that the ViewModelLocator constructor is always called on all platforms, it may be better to call it from code, eg from the App constructor in App.xaml.cs.