您的问题在这里吗？就是您仍在使用密码，即使密码为空。删除以下行：

Your problem here is that you're still using a password, even though it is blank. Remove this line:

new PasswordAuthenticationMethod(username, ""), 

这对我来说很完美：

var pk = new PrivateKeyFile(yourkey);
var keyFiles = new[] { pk };

var methods = new List<AuthenticationMethod>();
methods.Add(new PrivateKeyAuthenticationMethod(UserName, keyFiles));

var con = new ConnectionInfo(HostName, Port, UserName, methods.ToArray());