Use a new ssh connection using another established connection with SSH.NET [duplicate]

I have a target computer which can be accessed only with SSH, I do not have a direct connection, so I need to connect through another SSH machine.

Until now, I connect with putty (SSH) to machine A and then when I am logged in I SSH the machine B.

I'm trying to create an application that will run a script in machine B and I use SSH.NET, here is my code:

using (var client = new SshClient("hostMachineA", "usernameMachineA", "passwordMachineA"))
{
    client.Connect();
    try
    {
        if (client.IsConnected)
        {
            using (var terminalConnection = new SshClient("hostMachineB", "usernameMachineB", "passwordMachineB"))
            {
                terminalConnection.Connect();
                var command = terminalConnection.CreateCommand("ls -ltr");
                command.Execute();
                MessageBox.Show(command.Result);
                terminalConnection.Disconnect();
            }
        }

        client.Disconnect();
    }
    catch (Exception command)
    {
        MessageBox.Show(command.Message);
    }
}     

The problem is that my application connects to Machine A but it cannot establish connection with Machine B, it tries to create a new connection not using the connection which is already established from Machine A.

Any idea?