File UpLoad/Download Using serv-U C#

There are many tools/ways to programmatically upload

Use FTP Client, like Robo-FTP, WinSCP both of which have their own built-in scripting and API

Use FTP Clinet like SSIS using legacy DTS calls for sFTP 

But these suggestions are taking your question as written, perhaps some more details as to your objectives and chanllenges?

Thanks for Your response, Whereas I have already tried WinSCP and SSIS. If you notice the URL being given is https:// not ftp://

so the actual communication is happening on 443 port not on 990 or 21,22.

Well, although I've not done this exact task, seems like well walked path
Here's snip of WinSCP onto port 443, once set, Test connecting manually IF all good then call winSCP API 

Thanks, connection error . 

If the host is not configured by you, then the Host Admin should provide you w/protocol & encryption type