Singleton Design Pattern active and practical: single request vs single thread

/// <Summary> ///  Only the class of the unique instance exists during the Web request.  ///  Lazy is used.  /// </Summary>  Public class  Singletonperrequest { Public object Data; Public static readonly string Key = "Singletonperrequest. Key" ; Public static  Singletonperrequest Current {Get { Singletonperrequest Instance = ( Singletonperrequest ) Httpcontext . Current. items [Key]; If (Instance = Null ) {Instance = New  Singletonperrequest (); Httpcontext . Current. items [Key] = instance ;} Return Instance ;}}}/// <Summary> ///  Only a unique instance class exists in an execution thread.  ///  Lazy is used.  /// </Summary>  Public class  Singletonperthread { Public object Data; Public static readonly string Key = "Singletonperthread. Key" ; Public static  Singletonperthread Current { Get { Singletonperthread Instance = ( Singletonperthread ) Callcontext . Getdata (key ); If (Instance = Null ) {Instance = New  Singletonperthread (); Callcontext . Setdata (Key, instance );} Return Instance ;}}}

This is just an example. You can change it to a generic class to write a saferCode.

In addition, callcontext can be transplanted in Web/win, so the second scheme is also recommended in web.