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Technosoftware/DaAeHdaClient.Com/ConnectionPoint.cs

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+#region Copyright (c) 2011-2023 Technosoftware GmbH. All rights reserved
+//-----------------------------------------------------------------------------
+// Copyright (c) 2011-2023 Technosoftware GmbH. All rights reserved
+// Web: https://www.technosoftware.com 
+// 
+// The source code in this file is covered under a dual-license scenario:
+//   - Owner of a purchased license: SCLA 1.0
+//   - GPL V3: everybody else
+//
+// SCLA license terms accompanied with this source code.
+// See SCLA 1.0: https://technosoftware.com/license/Source_Code_License_Agreement.pdf
+//
+// GNU General Public License as published by the Free Software Foundation;
+// version 3 of the License are accompanied with this source code.
+// See https://technosoftware.com/license/GPLv3License.txt
+//
+// This source code is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.
+//-----------------------------------------------------------------------------
+#endregion Copyright (c) 2011-2023 Technosoftware GmbH. All rights reserved
+
+#region Using Directives
+using System;
+using Technosoftware.OpcRcw.Comn;
+#endregion
+
+namespace Technosoftware.DaAeHdaClient.Com
+{
+    /// <summary>
+    /// Adds and removes a connection point to a server.
+    /// </summary>
+    internal class ConnectionPoint : IDisposable
+    {
+        /// <summary>
+        /// The COM server that supports connection points.
+        /// </summary>
+		private IConnectionPoint server_;
+
+        /// <summary>
+        /// The id assigned to the connection by the COM server.
+        /// </summary>
+		private int cookie_;
+        
+        /// <summary>
+        /// The number of times Advise() has been called without a matching Unadvise(). 
+        /// </summary>
+		private int refs_;
+        
+        /// <summary>
+        /// Initializes the object by finding the specified connection point.
+        /// </summary>
+        public ConnectionPoint(object server, Guid iid)
+        {
+            ((IConnectionPointContainer)server).FindConnectionPoint(ref iid, out server_);
+        }
+
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public void Dispose()
+        {
+            if (server_ != null)
+            {
+                while (Unadvise() > 0)
+                {
+                }
+                try
+                {
+                    Utilities.Interop.ReleaseServer(server_);
+                }
+                catch
+                {
+                    // Ignore. COM Server probably no longer connected
+                }
+
+                server_ = null;
+            }
+        }
+
+        /// <summary> 
+        /// The cookie returned in the advise call. 
+        /// </summary> 
+        public int Cookie => cookie_;
+
+        //=====================================================================
+        // IConnectionPoint
+
+        /// <summary>
+        /// Establishes a connection, if necessary and increments the reference count.
+        /// </summary>
+        public int Advise(object callback)
+        {
+            if (refs_++ == 0) server_.Advise(callback, out cookie_);
+            return refs_;
+        }
+
+        /// <summary>
+        /// Decrements the reference count and closes the connection if no more references.
+        /// </summary>
+        public int Unadvise()
+        {
+            if (--refs_ == 0) server_.Unadvise(cookie_);
+            return refs_;
+        }
+    }
+}