I'm able to connect to sftp site using username and password by using below code:
FtpWebRequest reqFTP;
reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpURI + "/" + clientFolder + "/"));
reqFTP.UseBinary = true;
reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
But I'm not able to connect to sftp using username and .ppk file (putty private key file) and no password by using in built library of c#. Can you please help me by giving a small example to conner to sftp using .ppk file, I don't want to use third party library.