using System.Net.NetworkInformation;
private void button2_Click(object sender, EventArgs e)

{

    string remoteMachineNameOrIP = "127.0.0.1";

    int timeOut = 5;

    Ping ping = new Ping();

    // Pinging remote maching

    PingReply reply = ping.Send(remoteMachineNameOrIP, timeOut);

    // Displaying the result

    StringBuilder sb = new StringBuilder();

    sb.Append("Address:" + reply.Address.ToString());

    sb.Append("\nStatus:" + reply.Status.ToString());

    sb.Append("\nRoundtripTime:" + reply.RoundtripTime.ToString());

    MessageBox.Show(sb.ToString(), "Ping Result: " + remoteMachineNameOrIP);

}
منبع : http://www.dotnetspider.com/code/C-245-Ping-remote-computer-network.aspx