A Storyboard's target/targetname set in code is ignored on a call to storyboard.Begin():

        DoubleAnimation d = new DoubleAnimation();
        d.Duration = new Duration(TimeSpan.FromSeconds(2));
        d.To = 200;

        Storyboard sb = new Storyboard();
        sb.Children.Add(d);

        Storyboard.SetTarget(sb, CodeButton);
        Storyboard.SetTargetProperty(sb, new PropertyPath("Width"));
        Storyboard.SetTargetName(sb, "CodeButton");

        Debug.Assert(CodeButton.Name == "CodeButton");
        Debug.Assert(Storyboard.GetTarget(sb) == CodeButton);
        Debug.Assert(Storyboard.GetTargetProperty(sb).Path == "Width");
        Debug.Assert(Storyboard.GetTargetName(sb) == "CodeButton");

        sb.Begin();

In the above code snippet all assertions pass, but the call to Begin() fails with a log output of: ""Cannot Begin Storyboard, Target not found". Manually specifying the target "sb.Begin(CodeButton)" does work.