<UserControl x:Class="WpfApplication5.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d" Height="324" Width="506" Loaded="UserControl_Loaded">
<UserControl.Style>
<Style TargetType="UserControl">
<Style.Triggers>
<Trigger Property="Visibility" Value="Visible">
<Trigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Width" From="0" To="500" Duration="0:0:1" FillBehavior="HoldEnd" AutoReverse="False" />
<DoubleAnimation Storyboard.TargetProperty="Height" From="0" To="500" Duration="0:0:2" FillBehavior="HoldEnd" AutoReverse="False"/>
</Storyboard>
</BeginStoryboard>
</Trigger.EnterActions>
</Trigger>
</Style.Triggers>
</Style>
</UserControl.Style>
<Grid x:Name="grid">
<TextBox Text="aaaaaaaaaaaaaa" />
</Grid>
</UserControl>