Thank you for writing.
To show scrollbars when you resize the window the splitcontainer and the panels inside must be docked. Being docked they will change their size whenever their parent changes their size. This means that the RadPageView should be docked.
About your concern related to the black lines - you should subscribe to the Scroll event of the split panel and call the Invalidate method of that panel.
sender, ScrollEventArgs e)
You can use this method for other panels too.
I hope this helps.
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