help me to write a function in c#.net core that add user to exchange using novell library or any library that could do it . the point is that I need run my code on linux.
I assume you're talking about on premises Exchange (not Exchange Online, or Office 365).
You can't do this from Linux unfortunately.
Exchange does have a web service, but it cannot be used to create mailboxes.
The only way to create mailboxes in Exchange is to use PowerShell commands. This isn't terribly easy either. I have automated mailbox creation in C#, and I had to call the PowerShell commands from C# (and it has a ton of weird quirks - it's awful). But that, of course, can only be done on Windows.