Hook up the CategoryViewModel in the Shell

This is a very short step, but we now can hook the new Category UserControl into the Shell. We need two things to do:

Create a method to invoke the category editor.
On application start activate the CategoryViewModel and CategoryView in the shell.

Invoke the category editor

In the ShellViewModel we create a new method:

    public Task EditCategories()
      {
      var viewmodel = IoC.Get<CategoryViewModel>();
      return ActivateItemAsync(viewmodel, new CancellationToken());
      }

IoC stands for Inversion of Control. In a later section, you will see how you can set up a container. Here the default implementation is used. If you have a close look at the internals of the BootstrapperBase class, you may see it does not use a container, but in the end calls the .Net Activator class.

The second line calls ActivateItemAsync, which is a Caliburn.Micro method that activates a user control in a contentcontrol <ContentControl x:Name="ActiveItem" Margin="20"/> in the ShellView Make sure to use ActiveItem as the name for the ContentControl because Caliburn.Micro needs this naming convention.

A final comment, note an asynchronous invocation is used.

Activate `EditCategories()` on application startup

Once the ShellView is loaded, it is possible to show the contents of the contentcontrol. Thus, you can do it by adding this asynchronous method th the ShellViewModel

    protected async override void OnViewLoaded(object view)
      {
      base.OnViewLoaded(view);
      await EditCategories();
      }

One thing you need to remember: Do NOT use protected async override Task OnViewLoaded(object view) as you might think. The Task as return type will not work in this situation.

Summary

The ShellViewModel may now look like this:

using System.Threading;
using System.Threading.Tasks;

namespace Caliburn.Micro.Tutorial.Wpf.ViewModels
  {
  public class ShellViewModel : Conductor<object>
    {

    protected async override void OnViewLoaded(object view)
      {
      base.OnViewLoaded(view);
      await EditCategories();
      }


    public async Task EditCategories()
      {
      var viewmodel = IoC.Get<CategoryViewModel>();
      await ActivateItemAsync(viewmodel, new CancellationToken());
      }
    }
  }

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Hook up the CategoryViewModel in the Shell