PDFOffice_Windows_exe/PDF Office/Views/MainContent.xaml

<UserControl
    x:Class="PDF_Office.Views.MainContent"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:cus="clr-namespace:PDF_Office.CustomControl"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
    xmlns:local="clr-namespace:PDF_Office.Views"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:prism="http://prismlibrary.com/"
    xmlns:viewmodels="clr-namespace:PDF_Office.ViewModels"
    d:DataContext="{d:DesignInstance Type=viewmodels:MainContentViewModel}"
    d:DesignHeight="450"
    d:DesignWidth="800"
    prism:ViewModelLocator.AutoWireViewModel="True"
    mc:Ignorable="d">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Unloaded">
            <prism:InvokeCommandAction Command="{Binding UnLoaded}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <Grid>
        <ContentControl Name="ContentMain" prism:RegionManager.RegionName="{Binding MainContentRegionName}" />
    </Grid>
</UserControl>