mcs/class/System.ComponentModel.Composition/src/ComponentModel/System/ComponentModel/Composition/ReflectionModel/ExportingMember.cs

   1 // -----------------------------------------------------------------------\r
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.\r
   3 // -----------------------------------------------------------------------\r
   4 using System;\r
   5 using System.ComponentModel.Composition.Hosting;\r
   6 using System.ComponentModel.Composition.Primitives;\r
   7 using System.Globalization;\r
   8 using System.Reflection;\r
   9 using Microsoft.Internal;\r
  10 using System.Threading;\r
  11 \r
  12 namespace System.ComponentModel.Composition.ReflectionModel\r
  13 {\r
  14     internal class ExportingMember\r
  15     {\r
  16         private readonly ExportDefinition _definition;\r
  17         private readonly ReflectionMember _member;\r
  18         private object _cachedValue = null;\r
  19         private volatile bool _isValueCached = false;\r
  20 \r
  21         public ExportingMember(ExportDefinition definition, ReflectionMember member)\r
  22         {\r
  23             Assumes.NotNull(definition, member);\r
  24 \r
  25             this._definition = definition;\r
  26             this._member = member;\r
  27         }\r
  28 \r
  29         public bool RequiresInstance\r
  30         {\r
  31             get { return _member.RequiresInstance; }\r
  32         }\r
  33 \r
  34         public ExportDefinition Definition\r
  35         {\r
  36             get { return _definition; }\r
  37         }\r
  38 \r
  39         public object GetExportedValue(object instance, object @lock)\r
  40         {\r
  41             this.EnsureReadable();\r
  42 \r
  43             if (!this._isValueCached)\r
  44             {\r
  45                 object exportedValue;\r
  46                 try\r
  47                 {\r
  48                     exportedValue = this._member.GetValue(instance);\r
  49                 }\r
  50                 catch (TargetInvocationException exception)\r
  51                 {   // Member threw an exception. Avoid letting this \r
  52                     // leak out as a 'raw' unhandled exception, instead,\r
  53                     // we'll add some context and rethrow.\r
  54 \r
  55                     throw new ComposablePartException(\r
  56                         CompositionErrorId.ReflectionModel_ExportThrewException,\r
  57                         String.Format(CultureInfo.CurrentCulture,\r
  58                             Strings.ReflectionModel_ExportThrewException,\r
  59                             this._member.GetDisplayName()),\r
  60                         Definition.ToElement(),\r
  61                         exception.InnerException);\r
  62                 }\r
  63 \r
  64                 lock (@lock)\r
  65                 {\r
  66                     if (!this._isValueCached)\r
  67                     {\r
  68                         this._cachedValue = exportedValue;\r
  69                         Thread.MemoryBarrier();\r
  70 \r
  71                         this._isValueCached = true;\r
  72                     }\r
  73                 }\r
  74             }\r
  75 \r
  76             return this._cachedValue;\r
  77         }\r
  78 \r
  79         private void EnsureReadable()\r
  80         {\r
  81             if (!this._member.CanRead)\r
  82             {   // Property does not have a getter\r
  83 \r
  84                 throw new ComposablePartException(\r
  85                     CompositionErrorId.ReflectionModel_ExportNotReadable,\r
  86                     String.Format(CultureInfo.CurrentCulture, \r
  87                         Strings.ReflectionModel_ExportNotReadable,\r
  88                         this._member.GetDisplayName()),\r
  89                     Definition.ToElement());\r
  90             }\r
  91         }\r
  92     }\r
  93 }\r