class/System.ComponentModel.Composition/src/Composition.Initialization/System/ComponentModel/Composition/Hosting/CompositionHost.cs

   1 // -----------------------------------------------------------------------
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.
   3 // -----------------------------------------------------------------------
   4 using System;
   5 using System.Globalization;
   6 using System.Threading;
   7 using System.ComponentModel.Composition.Primitives;
   8 namespace System.ComponentModel.Composition.Hosting
   9 {
  10     public static class CompositionHost
  11     {
  12         // Field is internal only to assist in testing
  13         internal static CompositionContainer _container = null;
  14         private static object _lockObject = new object();
  15
  16         /// <summary>
  17         ///     This method can be used to initialize the global container used by <see cref="CompositionInitializer.SatisfyImports(object)"/>
  18         ///     in case where the default container doesn't provide enough flexibility.
  19         ///
  20         ///     If this method is needed it should be called exactly once and as early as possible in the application host. It will need
  21         ///     to be called before the first call to <see cref="CompositionInitializer.SatisfyImports(object)"/>
  22         /// </summary>
  23         /// <param name="container">
  24         ///     <see cref="CompositionContainer"/> that should be used instead of the default global container.
  25         /// </param>
  26         /// <exception cref="ArgumentNullException">
  27         ///     <paramref name="container"/> is <see langword="null"/>.
  28         /// </exception>
  29         /// <exception cref="InvalidOperationException">
  30         ///     Either <see cref="Initialize(CompositionContainer)" /> or <see cref="Initialize(ComposablePartCatalog[])" /> has already been called or someone has already made use of the global
  31         ///     container via <see cref="CompositionInitializer.SatisfyImports(object)"/>. In either case you need to ensure that it
  32         ///     is called only once and that it is called early in the application host startup code.
  33         /// </exception>
  34         public static void Initialize(CompositionContainer container)
  35         {
  36             if (container == null)
  37             {
  38                 throw new ArgumentNullException("container");
  39             }
  40
  41             CompositionContainer globalContainer = null;
  42             bool alreadyCreated = TryGetOrCreateContainer(() => container, out globalContainer);
  43
  44             if (alreadyCreated)
  45             {
  46                 throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture,
  47                     Strings.InvalidOperationException_GlobalContainerAlreadyInitialized));
  48             }
  49         }
  50
  51         /// <summary>
  52         ///     This method can be used to initialize the global container used by <see cref="CompositionInitializer.SatisfyImports(object)"/>
  53         ///     in case where the default container doesn't provide enough flexibility.
  54         ///
  55         ///     If this method is needed it should be called exactly once and as early as possible in the application host. It will need
  56         ///     to be called before the first call to <see cref="CompositionInitializer.SatisfyImports(object)"/>
  57         /// </summary>
  58         /// <param name="catalogs">
  59         ///     An array of <see cref="ComposablePartCatalog"/> that should be used to initialize the <see cref="CompositionContainer"/> with.
  60         /// </param>
  61         /// <exception cref="ArgumentNullException">
  62         ///     <paramref name="catalogs"/> is <see langword="null"/>.
  63         /// </exception>
  64         /// <exception cref="InvalidOperationException">
  65         ///     Either <see cref="Initialize(CompositionContainer)" /> or <see cref="Initialize(ComposablePartCatalog[])" />has already been called or someone has already made use of the global
  66         ///     container via <see cref="CompositionInitializer.SatisfyImports(object)"/>. In either case you need to ensure that it
  67         ///     is called only once and that it is called early in the application host startup code.
  68         /// </exception>
  69         public static CompositionContainer Initialize(params ComposablePartCatalog[] catalogs)
  70         {
  71             AggregateCatalog aggregateCatalog = new AggregateCatalog(catalogs);
  72             CompositionContainer container = new CompositionContainer(aggregateCatalog);
  73             try
  74             {
  75                 CompositionHost.Initialize(container);
  76             }
  77             catch
  78             {
  79                 container.Dispose();
  80
  81                 // NOTE : this is important, as this prevents the disposal of the catalogs passed as input arguments
  82                 aggregateCatalog.Catalogs.Clear();
  83                 aggregateCatalog.Dispose();
  84
  85                 throw;
  86             }
  87
  88             return container;
  89         }
  90
  91
  92
  93         internal static bool TryGetOrCreateContainer(Func<CompositionContainer> createContainer, out CompositionContainer globalContainer)
  94         {
  95             bool alreadyCreated = true;
  96             if (_container == null)
  97             {
  98                 var container = createContainer.Invoke();
  99                 lock (_lockObject)
 100                 {
 101                     if (_container == null)
 102                     {
 103                         Thread.MemoryBarrier();
 104                         _container = container;
 105                         alreadyCreated = false;
 106                     }
 107                 }
 108             }
 109             globalContainer = _container;
 110             return alreadyCreated;
 111         }
 112     }
 113 }