about SFTP file transfers in .NET search existing files on winscp

How to search existing files on winscp?
and What do you mean by that
winscp.StandardInput.WriteLine ("ls");
thank you very much!

Are you asking for to search file an a remote server using WinSCP .NET assembly?
You can use Session.EnumerateRemoteFiles:
https://winscp.net/eng/docs/library_session_enumerateremotefiles
See also this example:
https://winscp.net/eng/docs/library_example_recursive_search_text