WPF Animation Help

I'm new to WPF and I'm working on making a custom application to display photos. I'm experimenting with transitions currently. I have successfully created fade in/fade out, crossfade, and zoom in effects. I would like to also have a wipe affect. I found the following code that shows how to use the markup language to do it. I would like to take this code and put it into VB and do it all in the backend. I'm getting tripped up on the brush objects and the double animation objects controlling the brush.

Can anyone demonstrate how to do something like this in code?

<Window x:Class="LearnWPF.WipeEffect.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="LearnWPF.WipeEffect" Height="500" Width="700" Name="mainWindow"
    >
    <Grid>
      <Image Source="Images/UFO.jpg" />
      <Image Source="Images/ladder.jpg">
        <Image.OpacityMask>
          <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
              <GradientStop Offset="0" Color="Black" x:Name="BlackStop"/>
              <GradientStop Offset="0" Color="Transparent" x:Name="TransparentStop"/>
          </LinearGradientBrush>
        </Image.OpacityMask>
      </Image> 
    </Grid>
  <Window.Triggers>
    <EventTrigger RoutedEvent="Window.Loaded">
      <EventTrigger.Actions>
        <BeginStoryboard>
          <Storyboard>
            <DoubleAnimation Storyboard.TargetName="TransparentStop"
                             Storyboard.TargetProperty="Offset" By="1"  Duration="0:0:2"   />
            <DoubleAnimation Storyboard.TargetName="BlackStop"
                             Storyboard.TargetProperty="Offset" By="1" Duration="0:0:2"
                             BeginTime="0:0:0.05" />
          </Storyboard>
        </BeginStoryboard>
      </EventTrigger.Actions>
    </EventTrigger>
  </Window.Triggers>
</Window>