c# - Web Service Singleton object problem -

i creating singleton object in first request web service , keeping in memory.

this works fine first few seconds. if make request 5 minutes later, can see singleton object created again? singleton object getting disposed after x no of minutes ?

how can make increase life-time of object forever ?

    public sealed class singleton     {         static serverinstance instance = null;         static readonly object padlock = new object();          singleton() {         }          public static serverinstance instance {             {                 lock (padlock) {                     if (instance == null) {                         instance = new serverinstance();                     }                     return instance;                 }             }         }         ~singleton()         {           #if debug                   exceptionfactory.fatal("~singleton() called!");           #endif         }     }       [webmethod]     public string onreceiveevent(string objectxmldata, string objecttype) {          if (!singleton.instance.initservercomplete) {             initserver();         }         return singleton.instance.onreceiveevent(objectxmldata, objecttype);     }    public void initserver() {             if (!singleton.instance.initservercomplete) {                 singleton.instance.initserver();                 singleton.instance.initservercomplete = true;                  gc.keepalive(singleton.instance);             }         } 

there can no of reasons thinking aspnet process recyling.