why all Session value reset when write file

I have some session value, if I run "PrintLog", all session value will delete, why? Thank you very much





Step 1:


a.aspxSession["test"] = "abc";


Session["test2"] = "def";Step 2


b.aspxResponse.Write (Session["test"].ToString()); // Retrun abc


Response.Write (Session["test2"].ToString()); // Retrun defStep 3


c.aspxPrintLog("a.txt", "abc");Step 4


b.aspxResponse.Write (Session["test"].ToString()); // Retrun NULL


Response.Write (Session["test2"].ToString()); // Retrun NULLPlease Help, I am use C#.net, VS.net 2002, Windows 2000





Thank you very much











--------- code ------------- private void PrintLog(string sLogFileName, string sMessage)


{


FileStream fs = File.Open(sLogFileName, FileMode.Append, ...