"Problems encountered at work" Dictionary an add operation to make the report go beyond the bounds of the array

The main function of the problem code is to record the execution time of the page:

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSYSTEM.WEB.MVC;6 usingtcwireless.utility;7 usingSystem.Threading;8 usingTCBase.EagleEye.Metric;9 Ten namespaceTCWireless.Controller.BaseController One { A      Public classTimefilter:actionfilterattribute -     { -          Public stringName {Get;Set; } the         //Create a dictionary to record the start time, and key is the thread ID of the access. -         Private ReadOnlydictionary<int, datetime> _start =Newdictionary<int, datetime>(); -          Public Override voidonactionexecuting (actionexecutingcontext filtercontext) -         { +             //filter out Childaction, because childaction is actually not a separate page -             if(filtercontext.ischildaction)return; +             varCurrentthreadid =Thread.CurrentThread.ManagedThreadId; A             Try at             { -                 if(!_start. ContainsKey (Currentthreadid)) -                 { - _start. ADD (Currentthreadid, datetime.now); -                 } -             } in             Catch(Exception ex) -             { toLogwrapper.addinfo ("Mobilehotel","Timefilter","onactionexecuting", ex); +             } -         } the          Public Override voidonresultexecuted (resultexecutedcontext filtercontext) *         { $             varCurrentthreadid =Thread.CurrentThread.ManagedThreadId;Panax Notoginseng             if(!_start. ContainsKey (Currentthreadid))return; -             Try the             { +                 //Calculate the current page access time A                 varCostseconds = (DateTime.Now-_start[currentthreadid]). TotalMilliseconds; the                 intValue =Convert.ToInt32 (costseconds); + MetricClient.Instance.LogTiming (Name, value); -             } $             Catch(Exception ex) $             { -Logwrapper.addinfo ("Mobilehotel","Timefilter","onresultexecuted", ex); -             } the             finally -             {Wuyi _start. Remove (currentthreadid); the             } -         } Wu     } -}

The problem appears on line 26th.

Then Baidu found other people also found such problems, because dictionnary is multithreaded insecure. Need to add a lock

"Problems encountered at work" Dictionary an add operation to make the report go beyond the bounds of the array