ComEventsHelper.cs

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using System.Runtime.Versioning;
 
namespace System.Runtime.InteropServices;
 
[SupportedOSPlatform("windows")]
public static class ComEventsHelper
{
    public static void Combine(object rcw, Guid iid, int dispid, Delegate d)
    {
        lock (rcw)
        {
            ComEventsInfo comEventsInfo = ComEventsInfo.FromObject(rcw);
            ComEventsSink comEventsSink = comEventsInfo.FindSink(ref iid) ?? comEventsInfo.AddSink(ref iid);
            ComEventsMethod comEventsMethod = comEventsSink.FindMethod(dispid) ?? comEventsSink.AddMethod(dispid);
            comEventsMethod.AddDelegate(d);
        }
    }
 
    public static Delegate? Remove(object rcw, Guid iid, int dispid, Delegate d)
    {
        lock (rcw)
        {
            ComEventsInfo comEventsInfo = ComEventsInfo.Find(rcw);
            if (comEventsInfo == null)
            {
                return null;
            }
            ComEventsSink comEventsSink = comEventsInfo.FindSink(ref iid);
            if (comEventsSink == null)
            {
                return null;
            }
            ComEventsMethod comEventsMethod = comEventsSink.FindMethod(dispid);
            if (comEventsMethod == null)
            {
                return null;
            }
            comEventsMethod.RemoveDelegate(d);
            if (comEventsMethod.Empty)
            {
                comEventsMethod = comEventsSink.RemoveMethod(comEventsMethod);
            }
            if (comEventsMethod == null)
            {
                comEventsSink = comEventsInfo.RemoveSink(comEventsSink);
            }
            if (comEventsSink == null)
            {
                Marshal.SetComObjectData(rcw, typeof(ComEventsInfo), null);
                GC.SuppressFinalize(comEventsInfo);
            }
            return d;
        }
    }
}