Session Duration in ASP.NET C# -

i new asp.net , trying find session duration page load time time click button end session. trying use datetime , timespan, problem datetime value generated in 1 event cannot accessed in other event.

'// code  using system; using system.collections.generic; using system.linq; using system.web; using system.web.ui; using system.web.ui.webcontrols;  namespace webapplication17 { public partial class webform1 : system.web.ui.page  {     //datetime tstart, tnow, tend;       protected void page_load(object sender, eventargs e)     {       }      // button start session     public void begin_click(object sender, eventargs e)     {         datetime tstart = datetime.now;         sesstart.text = tstart.tostring();     }     // display present time in updatepanel using ajax timer           protected void timer1_tick(object sender, eventargs e)     {         datetime tnow = datetime.now;         prestime.text = tnow.tostring();      }     // button end session     public void end_click(object sender, eventargs e)     {         datetime tend = datetime.now;      //the problem exists here. value of tstart taken default                         timespan tspan = tend - tstart;           sesend.text = tend.tostring();         dur.text = convert.tostring(tstart);            }       }       }' 

you can use session variable overcome problem. need set session variable value @ time of begin_click event invoked.

 public void begin_click(object sender, eventargs e) {     datetime tstart = datetime.now;     sesstart.text = tstart.tostring();     session["beginend"] = tstart; } 

and time of end_click clicked

public void end_click(object sender, eventargs e) {     datetime tend = datetime.now;     datetime tstart = convert.todatetime(session["beginend"]);     timespan tspan = tend - tstart;     sesend.text = tend.tostring();     dur.text = convert.tostring(tstart);  }