> For the complete documentation index, see [llms.txt](https://yanxiaodi.gitbook.io/xamarin-mvvmcross-handbook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yanxiaodi.gitbook.io/xamarin-mvvmcross-handbook/using-mvvmcross-to-create-your-first-xamarin-app/creating-the-uwp-project/updating-the-app.xaml.cs-and-the-app.xaml.md).
# Updating the App.xaml.cs and the App.xaml
Open the `App.xaml.cs` file and replace the content with the following code:
```csharp
using MvvmCross.Platforms.Uap.Core;
using MvvmCross.Platforms.Uap.Views;
namespace MvvmCrossDemo.Uwp
{
///
/// Provides application-specific behavior to supplement the default Application class.
///
sealed partial class App
{
///
/// Initializes the singleton application object. This is the first line of authored code
/// executed, and as such is the logical equivalent of main() or WinMain().
///
public App()
{
this.InitializeComponent();
}
}
public abstract class UWPApplication : MvxApplication, Core.App>
{
}
}
```
You can find the codes here: .
`UwpApplication` is an abstract class that contains the necessary information to run the `MvvmCross` framework. We can also use our customized `Setup` class instead of the default `Setup` class. Just keep it as simple as possible at the moment.
Now it is time to update the `App.xaml`. We need to modify the `XAML` code to make sure the `App` class inherits from the `UwpApplication`. You can find it here: . Replace the content of the file with the following code:
```markup
Hello World!
```