[Avalonia] Problems setting ItemSource of ListBox from Codebehind

So the Problem im having is that when trying to set the The ItemSource of the SelectableServers ListBox (see the BlazeBin) its not reflecting in the UI. Ive verified that the callback that i made runs and that the Server gets added to the Servers list. the weird thing is that when i set the Background Color for the Parent Panel it works. Just the Updating of the ItemSource doesn't