System.Web.HttpContext.Trace is of System.Web.TraceContext type, which only writes the page (if <%@ page trace="true" %>) and output to a trace viewer application (Trace.axd)
System.Diagnostics.Trace is more generic and powerful
>>>因为文件已经存在,不能再添加一个同名的文件
only open the file once or open a FileStream with System.IO.FileMode.Create and use it as the parameter for TextWriterTraceListener
>>>中的 AbsolutePathToYourFile 能不能改成相对路径啊??
no, you can always use Server.MapPath to convert it to an absolute path