public class AdViewRenderer : ViewRenderer<AdControlView, UWPAdView>
{
    protected override void OnElementChanged(ElementChangedEventArgs<AdControlView> e)
    {
        base.OnElementChanged(e);

        if (null == Control && e.NewElement != null)
        {
            UWPAdView ad = new UWPAdView();
            SetNativeControl(ad);
        }
    }
}

<UserControl
    x:Class="Sample.UWP.Helpers.UWPAdView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:aduwp="using:Microsoft.Advertising.WinRT.UI"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    d:DesignHeight="300"
    d:DesignWidth="400"
    mc:Ignorable="d">

    <Grid>
        <aduwp:AdControl
            Width="640"
            Height="100"
            HorizontalAlignment="Stretch"
            AdUnitId="myadunitid"
            ApplicationId="myappid"
            AutoRefreshIntervalInSeconds="30"
            ErrorOccurred="AdControl_ErrorOccurred"
            IsAutoRefreshEnabled="True" />
    </Grid>
</UserControl>