how to change the angle of an xaml wdf image angle parameter by VB.net code in runtime?

I have a image that transformed in design time to get it specific angle. XAML is like below.

<Image x:Name="Yelkovan" HorizontalAlignment="Left" Height="163" Margin="178,80,0,0" VerticalAlignment="Top" Width="14" Source="/k-yelkovan.png" RenderTransformOrigin="0.558,0.863">
            <Image.RenderTransform>
                <TransformGroup>
                    <ScaleTransform/>
                    <SkewTransform/>
                    <RotateTransform Angle="-30"/>
                    <TranslateTransform X="27.336" Y="-7.117"/>
                </TransformGroup>
            </Image.RenderTransform>
        </Image>

I want to set angle by vb.net code in runtime, ie when press a button, set its transform angle from -30 to ie : +45 deg only. How is this possible?

>Solution :

You can give your RotateTransform a name:

<RotateTransform x:Name="Rotation"  Angle="-30"/>

Then you can access it like a control:

Me.Rotation.Angle = -25