Loading dll problem

So, i try to contact my mysql database via my api and a lua plugin (dll), i use a web-request. I have errors and i tried to resolve them during 7 hours and it don’t work. i have source code of the dll and the module source code. Can you help me please ?

screenshot of the error:
https://gyazo.com/3edec577694e1f1b302b886bf6d70e81

Here is the archive with the module source code and the c# dll souce code.
https://mega.nz/#!bYVXAZBL!s2OAO5srUq5YhTroTudr866yAoueZgSCTJQC7WEqudw

Thanks in advence.