What is App.xaml in WPF project? Share on Facebook Share Share on TwitterTweet Share on LinkedIn Share App.xaml is the start up file or a boot strapper file which triggers your first XAML page from your WPF project. Share on Facebook Share Share on TwitterTweet Share on LinkedIn Share Related posts: What is XAML in WPF and why do we need it? Provide some instances where you have “xmlns:x” namespace in XAML ? What Is XAML? What are the benefits of MVVM?