Start\Stop processes in Task Manager on Windows server

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PowerShell

ASP.NET4

SshNet library for safe connection to Windows Server from asp.net. Now I ant to start\stop any process running on Task Manager. Is it done using PowerShell or any other way? If yes than how can I start PowerShell and than run command from asp.net

ConnectionInfo connectionInfo = new PasswordConnectionInfo(ip, port, userid, password);
    using (Renci.SshNet.SshClient client = new Renci.SshNet.SshClient(connectionInfo))
    {
        client.Connect();
        //What should I do here to open PowerShell
        var cmd = client.RunCommand("Get-Command");
        lbl.Text = "Output: " + cmd.Result;
        client.Disconnect();
    }

Running above code I am getting following error: AllowDesktopAccess failed. Unable to execute command or shell on remote system: Failed to Execute process

Does this mean that I cannot execute PowerShell command from asp.net?