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diff --git a/trunk/qpid/dotnet/Qpid.Client/Client/Closeable.cs b/trunk/qpid/dotnet/Qpid.Client/Client/Closeable.cs
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+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+using System;
+using Apache.Qpid.Messaging;
+
+namespace Apache.Qpid.Client
+{
+    /// <summary>Closeable provides monitoring of the state of a closeable resource; whether it is open or closed. It also provides a lock on which
+    /// attempts to close the resource from multiple threads can be coordinated.
+    ///
+    /// <p/><table id="crc"><caption>CRC Card</caption>
+    /// <tr><th> Responsibilities <th> Collaborations
+    /// <tr><td> Close (and clean-up) a resource.
+    /// <tr><td> Monitor the state of a closeable resource.
+    /// <tr><td> Synchronous attempts to close resource from concurrent threads.
+    /// </table>
+    /// </summary>
+    ///
+    /// <remarks>Poor encapsulation of the close lock. Better to completely hide the implementation, such that there is a method, e.g., DoSingleClose,
+    /// that sub-classes implement. Guaranteed to only be called by one thread at once, and iff the object is not already closed. That is, multiple
+    /// simultaneous closes will result in a single call to the real close method. Put the wait and condition checking loop in this base class.
+    /// </remarks>
+    public abstract class Closeable : ICloseable
+    {
+        /// <summary> Constant representing the closed state. </summary>
+        protected const int CLOSED = 1;
+
+        /// <summary> Constant representing the open state. </summary>
+        protected const int NOT_CLOSED = 2;
+
+        /// <summary> Used to ensure orderly closing of the object. </summary>
+        protected readonly object _closingLock = new object();
+
+        /// <summary> Indicates the state of this resource; open or closed. </summary>
+        protected int _closed = NOT_CLOSED;
+
+        /// <summary>
+        /// Checks the not closed.
+        /// </summary>
+        ///
+        /// <remarks>Don't like check methods that throw exceptions. a) it can come as a surprise without checked exceptions, b) it limits the 
+        /// callers choice, if the caller would prefer a boolean, c) it is not side-effect free programming, where such could be used. Get rid
+        /// of this and replace with boolean.</remarks>
+        protected void CheckNotClosed()
+        {
+            if (_closed == CLOSED)
+            {
+                throw new InvalidOperationException("Object " + ToString() + " has been closed");
+            }
+        }
+
+        /// <summary>Indicates whether this resource is closed.</summary>
+        /// <value><c>true</c> if closed; otherwise, <c>false</c>.</value>
+        public bool Closed
+        {
+            get
+            {
+                return _closed == CLOSED;
+            }
+        }
+
+        /// <summary> Close this resource. </summary>
+        public abstract void Close();
+    }
+}