How to resize / fill to window video

I have problem with resizing video in VLC control added in winforms.

What I have is this:

With two black bars on sides. I want to expand video to fill window even if it adds distortion to video. I tried to add change aspect ratio with command line arguments but with no luck like this (example):

LibVlc = new LibVLC(new string[] {"--aspect-ratio=4:3" });

TL:DR - I want to override VLC acpect ratio and video size, any suggestions ?

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