Hi it's very easy.it's not suitable raiseEvent in userControls.
you can do this.your mainWindow.xaml must be like following:
<my:one x:name="OneUserControl" buttonbase.click="Show" />
<my:two x:name="TwoUserControl" visibility="Hidden" />
your mainWindow.cs must be like :
private void Show(object sender,RoutedEventArgs e)
{
Button button=e.OriginalSource as Button;
if(button==null)
{
return ;
}
else
{
TwoUserControl.Visibility=Visibility.Visible;
}
}
GoodLuck