在加载其他图像的事件时更改图像源

I'm working with new MS technology UWP. I have 2 images in DataTemplate, CopyImage and MainImage. It's because of image flickering, when source is changed. So I would like to ask, how can I set the source of CopyImage, when event Loaded of MainImage is fired? In WPF I can use DataTriggers, but they are not in UWP. I want to do that in XAML, no in code-behind.I'm working with new MS technology UWP. I have