you can use following code if you want separate log files for each day
string vrCurrentDate = DateTime.Now.ToString("ddMMyyyy");
FileStream fs = new FileStream(AppDomain.CurrentDomain.BaseDirectory + "\\" + vrCurrentDate + ".txt", FileMode.OpenOrCreate, FileAccess.Write);
StreamWriter sw = new StreamWriter(fs);
sw.BaseStream.Seek(0, SeekOrigin.End);
sw.WriteLine(DateTime.Now.ToString() + " : " + Message);
sw.Flush();
sw.Close();
hope this will help you. "FileMode.OpenOrCreate" will create new file for each day if not created already otherwise it will update that existing file for that day