vue-java-tutorials/CSharp/WPFTutorial/WPF-26-MVVM/App.xaml

<prism:PrismApplication x:Class="WPF_26_MVVM.App"
                        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                        xmlns:prism="http://prismlibrary.com/">
    <prism:PrismApplication.Resources>
    </prism:PrismApplication.Resources>
</prism:PrismApplication>