OK, so remove the SshPrivateKeyPath.
You probably have the key set in your GUI session settings. While GUI will ignore the key, if you set it for non-SSH session, the .NET assembly is more strict.

hi,
i'm trying to connect to ftp site using .net assembly with session option c# code generated by winscp ui, as follow

// Set up session options
SessionOptions sessionOptions = new SessionOptions
{
Protocol = Protocol.Ftp,
HostName = "xxxxxxxxxx",
PortNumber = 21,
UserName = "xxxxxx",
Password = "xxxxx",
SshPrivateKeyPath = @"C:\Program Files\WinSCP\......PPK",
FtpMode = FtpMode.Active,
TimeoutInMilliseconds = 60000,
};

sessionOptions.AddRawSettings("ProxyHost", "xxx.xxx.xxx.xxx");
sessionOptions.AddRawSettings("ProxyPort", "1080");

using (Session session = new Session())
{
// Connect
session.Open(sessionOptions);

// Your code
}

I can connect with winscp ui but i get the error
SessionOptions.SshPrivateKeyPath is set, but SessionOptions.Protocol is neither Protocol.Sftp nor Protocol.Scp.
when i use .net assembly in c# application.

Some suggestion?

thanks