mcs/class/System.ComponentModel.Composition/src/ComponentModel/System/Lazy.cs

   1 // -----------------------------------------------------------------------\r
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.\r
   3 // -----------------------------------------------------------------------\r
   4 #if !CLR40\r
   5 using System;\r
   6 using System.Collections.Generic;\r
   7 using System.Linq;\r
   8 using System.Text;\r
   9 using System.Threading;\r
  10 using Microsoft.Internal;\r
  11 \r
  12 namespace System\r
  13 {\r
  14     public class Lazy<T>\r
  15     {\r
  16         private T _value = default(T);\r
  17         private volatile bool _isValueCreated = false;\r
  18         private Func<T> _valueFactory = null;\r
  19         private object _lock;\r
  20 \r
  21         public Lazy()\r
  22             : this(() => Activator.CreateInstance<T>())\r
  23         {\r
  24         }\r
  25 \r
  26         public Lazy(bool isThreadSafe)\r
  27             : this(() => Activator.CreateInstance<T>(), isThreadSafe)\r
  28         {\r
  29         }\r
  30 \r
  31         public Lazy(Func<T> valueFactory):\r
  32             this(valueFactory, true)\r
  33         {\r
  34         }\r
  35 \r
  36         public Lazy(Func<T> valueFactory, bool isThreadSafe)\r
  37         {\r
  38             Requires.NotNull(valueFactory, "valueFactory");\r
  39             if(isThreadSafe)\r
  40             {\r
  41                 this._lock = new object();\r
  42             }\r
  43 \r
  44             this._valueFactory = valueFactory;\r
  45         }\r
  46 \r
  47 \r
  48         public T Value\r
  49         {\r
  50             get\r
  51             {\r
  52                 if (!this._isValueCreated)\r
  53                 {\r
  54                     if(this._lock != null)\r
  55                     {\r
  56                         Monitor.Enter(this._lock);\r
  57                     }\r
  58 \r
  59                     try\r
  60                     {\r
  61                         T value = this._valueFactory.Invoke();\r
  62                         this._valueFactory = null;\r
  63                         Thread.MemoryBarrier();\r
  64                         this._value = value;\r
  65                         this._isValueCreated = true;\r
  66                     }\r
  67                     finally\r
  68                     {\r
  69                         if(this._lock != null)\r
  70                         {\r
  71                             Monitor.Exit(this._lock);\r
  72                         }\r
  73                     }\r
  74                 }\r
  75                 return this._value;\r
  76             }\r
  77         }\r
  78     }\r
  79 }\r
  80 #endif\r