In C# dovrebbe essere:

codice:
public static void Log(string logMessage)
{
    string logpath = HttpRuntime.AppDomainAppPath + "Log.txt";
    using (StreamWriter w = File.AppendText(logpath)) {
        w.Write(System.Environment.NewLine + "{0} {1}: {2}", DateTime.Now.tostring("dd/MM/yyyy"),                        DateTime.Now.ToLongTimeString(), logMessage);
        w.WriteLine("-------------------------------");
    }
}

domani lo provo