class/System.ComponentModel.Composition/src/ComponentModel/System/ComponentModel/Composition/Hosting/ImportEngine.EngineContext.cs

   1 // -----------------------------------------------------------------------
   2 // Copyright (c) Microsoft Corporation.  All rights reserved.
   3 // -----------------------------------------------------------------------
   4 using System;
   5 using System.Collections.Generic;
   6 using System.ComponentModel.Composition.Primitives;
   7 using System.Diagnostics;
   8 using System.Linq;
   9 using System.Runtime.CompilerServices;
  10 using Microsoft.Internal;
  11 using Microsoft.Internal.Collections;
  12
  13 namespace System.ComponentModel.Composition.Hosting
  14 {
  15     public partial class ImportEngine
  16     {
  17         /// <summary>
  18         ///     Used to wrap the start and stop of enforcing export changes don't
  19         ///     break required imports. This context is stored in a AtomicComposition.
  20         /// </summary>
  21         private class EngineContext
  22         {
  23             private ImportEngine _importEngine;
  24             private List<PartManager> _addedPartManagers = new List<PartManager>();
  25             private List<PartManager> _removedPartManagers = new List<PartManager>();
  26             private EngineContext _parentEngineContext;
  27
  28             public EngineContext(ImportEngine importEngine, EngineContext parentEngineContext)
  29             {
  30                 this._importEngine = importEngine;
  31                 this._parentEngineContext = parentEngineContext;
  32             }
  33
  34             public void AddPartManager(PartManager part)
  35             {
  36                 Assumes.NotNull(part);
  37                 if (!this._removedPartManagers.Remove(part))
  38                 {
  39                     this._addedPartManagers.Add(part);
  40                 }
  41             }
  42
  43             public void RemovePartManager(PartManager part)
  44             {
  45                 Assumes.NotNull(part);
  46                 if (!this._addedPartManagers.Remove(part))
  47                 {
  48                     this._removedPartManagers.Add(part);
  49                 }
  50             }
  51
  52             public IEnumerable<PartManager> GetAddedPartManagers()
  53             {
  54                 if (this._parentEngineContext != null)
  55                 {
  56                     return this._addedPartManagers.ConcatAllowingNull(this._parentEngineContext.GetAddedPartManagers());
  57                 }
  58                 return this._addedPartManagers;
  59             }
  60
  61             public IEnumerable<PartManager> GetRemovedPartManagers()
  62             {
  63                 if (this._parentEngineContext != null)
  64                 {
  65                     return this._removedPartManagers.ConcatAllowingNull(this._parentEngineContext.GetRemovedPartManagers());
  66                 }
  67                 return this._removedPartManagers;
  68             }
  69
  70             public void Complete()
  71             {
  72                 foreach (var partManager in this._addedPartManagers)
  73                 {
  74                     this._importEngine.StartSatisfyingImports(partManager, null);
  75                 }
  76
  77                 foreach (var partManager in this._removedPartManagers)
  78                 {
  79                     this._importEngine.StopSatisfyingImports(partManager, null);
  80                 }
  81             }
  82         }
  83     }
  84 }