src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsSink.cs

   1 // Licensed to the .NET Foundation under one or more agreements.
   2 // The .NET Foundation licenses this file to you under the MIT license.
   3 // See the LICENSE file in the project root for more information.
   4
   5
   6 /*============================================================
   7 **
   8 **
   9 ** Purpose: part of ComEventHelpers APIs which allow binding
  10 ** managed delegates to COM's connection point based events.
  11 **
  12 **/
  13
  14 using System;
  15 using System.Diagnostics;
  16
  17 namespace System.Runtime.InteropServices
  18 {
  19     // see code:ComEventsHelper#ComEventsArchitecture
  20     internal class ComEventsSink : ICustomQueryInterface
  21     {
  22         #region private fields
  23
  24         private Guid _iidSourceItf;
  25         private ComTypes.IConnectionPoint _connectionPoint;
  26         private int _cookie;
  27         private ComEventsMethod _methods;
  28         private ComEventsSink _next;
  29
  30         #endregion
  31
  32
  33         #region ctor
  34
  35         internal ComEventsSink(object rcw, Guid iid)
  36         {
  37             _iidSourceItf = iid;
  38             this.Advise(rcw);
  39         }
  40
  41         #endregion
  42
  43
  44         #region static members
  45
  46         internal static ComEventsSink Find(ComEventsSink sinks, ref Guid iid)
  47         {
  48             ComEventsSink sink = sinks;
  49             while (sink != null && sink._iidSourceItf != iid)
  50             {
  51                 sink = sink._next;
  52             }
  53
  54             return sink;
  55         }
  56
  57         internal static ComEventsSink Add(ComEventsSink sinks, ComEventsSink sink)
  58         {
  59             sink._next = sinks;
  60             return sink;
  61         }
  62
  63         internal static ComEventsSink RemoveAll(ComEventsSink sinks)
  64         {
  65             while (sinks != null)
  66             {
  67                 sinks.Unadvise();
  68                 sinks = sinks._next;
  69             }
  70
  71             return null;
  72         }
  73
  74         internal static ComEventsSink Remove(ComEventsSink sinks, ComEventsSink sink)
  75         {
  76             Debug.Assert(sinks != null, "removing event sink from empty sinks collection");
  77             Debug.Assert(sink != null, "specify event sink is null");
  78
  79             if (sink == sinks)
  80             {
  81                 sinks = sinks._next;
  82             }
  83             else
  84             {
  85                 ComEventsSink current = sinks;
  86                 while (current != null && current._next != sink)
  87                     current = current._next;
  88
  89                 if (current != null)
  90                 {
  91                     current._next = sink._next;
  92                 }
  93             }
  94
  95             sink.Unadvise();
  96
  97             return sinks;
  98         }
  99
 100         #endregion
 101
 102
 103         #region public methods
 104
 105         public ComEventsMethod RemoveMethod(ComEventsMethod method)
 106         {
 107             _methods = ComEventsMethod.Remove(_methods, method);
 108             return _methods;
 109         }
 110
 111         public ComEventsMethod FindMethod(int dispid)
 112         {
 113             return ComEventsMethod.Find(_methods, dispid);
 114         }
 115
 116         public ComEventsMethod AddMethod(int dispid)
 117         {
 118             ComEventsMethod method = new ComEventsMethod(dispid);
 119             _methods = ComEventsMethod.Add(_methods, method);
 120             return method;
 121         }
 122
 123         #endregion
 124
 125         private static Guid IID_IManagedObject = new Guid("{C3FCC19E-A970-11D2-8B5A-00A0C9B7C9C4}");
 126
 127         CustomQueryInterfaceResult ICustomQueryInterface.GetInterface(ref Guid iid, out IntPtr ppv)
 128         {
 129             ppv = IntPtr.Zero;
 130             if (iid == _iidSourceItf || iid == typeof(IDispatch).GUID)
 131             {
 132                 ppv = Marshal.GetComInterfaceForObject(this, typeof(IDispatch), CustomQueryInterfaceMode.Ignore);
 133                 return CustomQueryInterfaceResult.Handled;
 134             }
 135             else if (iid == IID_IManagedObject)
 136             {
 137                 return CustomQueryInterfaceResult.Failed;
 138             }
 139
 140             return CustomQueryInterfaceResult.NotHandled;
 141         }
 142
 143         #region private methods
 144
 145
 146         private void Advise(object rcw)
 147         {
 148             Debug.Assert(_connectionPoint == null, "comevent sink is already advised");
 149
 150             ComTypes.IConnectionPointContainer cpc = (ComTypes.IConnectionPointContainer)rcw;
 151             ComTypes.IConnectionPoint cp;
 152             cpc.FindConnectionPoint(ref _iidSourceItf, out cp);
 153
 154             object sinkObject = this;
 155
 156             cp.Advise(sinkObject, out _cookie);
 157
 158             _connectionPoint = cp;
 159         }
 160
 161         private void Unadvise()
 162         {
 163             Debug.Assert(_connectionPoint != null, "can not unadvise from empty connection point");
 164
 165             try
 166             {
 167                 _connectionPoint.Unadvise(_cookie);
 168                 Marshal.ReleaseComObject(_connectionPoint);
 169             }
 170             catch (System.Exception)
 171             {
 172                 // swallow all exceptions on unadvise
 173                 // the host may not be available at this point
 174             }
 175             finally
 176             {
 177                 _connectionPoint = null;
 178             }
 179         }
 180
 181         #endregion
 182     };
 183 }