Mongodb.Bson error

[PreCode]

Hello guys,

for the first 1000 lines i just didnt compile my server to .dll now where I wanted to switch, i just downloaded all the packaged I had via nuget. So good so far.

I followed this guide

 

Then I just added my stuff from before and now I have this error:
http://prntscr.com/kcywbo

I dont know what to do, I use net.core 2.0.

Edit: The file is there btw

Thanks for help.

Edited July 30, 2018 by PreCode