fast-log

public static void WriteLog(string message, string group = "")
{
    var logPath = System.IO.Path.Combine(System.AppDomain.CurrentDomain.BaseDirectory, "error-log");
    if (!System.IO.Directory.Exists(logPath)) { System.IO.Directory.CreateDirectory(logPath); }
    if (System.IO.File.Exists(logPath + "off.log")) { return; }
    var fileName = System.DateTime.Now.ToString("yyyy-MM-dd") + ".log";
    if (string.IsNullOrEmpty(group)) { group = "default"; } else { fileName = string.Concat(group, "-", fileName); }
    fileName = System.IO.Path.Combine(logPath, fileName);
    var sw = new System.IO.StreamWriter(fileName, true) { AutoFlush = true };
    var head = "[START]======[Group:" + group + "]======[Time:" + System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.FFF") + "]======" + "\r\n\r\n";
    var content = "[LOG]:" + message + "\r\n\r\n";
    var foot = "[END]======[Group:" + group + "]======\r\n\r\n";
    var msg = head + content + foot;
    sw.Write(msg);
    sw.Close();
}