You can use a Popup and a StoryBoard, like :
if (!StandardPopup.IsOpen)
{
StandardPopup.IsOpen = true;
var da = new DoubleAnimation
{
From = 0.0,
To = 1.0,
Duration = new Duration(TimeSpan.FromSeconds(2))
};
var sb = new Storyboard
{
Duration = TimeSpan.FromSeconds(4),
AutoReverse = true,
};
sb.Children.Add(da);
Storyboard.SetTarget(da, StandardPopup);
Storyboard.SetTargetProperty(da, "Opacity");
sb.Completed += delegate {if (StandardPopup.IsOpen) { StandardPopup.IsOpen = false; } };
sb.Begin();
}
XAML (change colors, location, size...):
<Popup VerticalOffset="20" HorizontalOffset="200" x:Name="StandardPopup">
<Border BorderBrush="{StaticResource ApplicationForegroundThemeBrush}"
CornerRadius="25"
Background="Gray"
BorderThickness="2" Width="200" Height="100">
<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock Text="This is a Popup" FontSize="24" HorizontalAlignment="Center"/>
</StackPanel>
</Border>
</Popup>