#region Apache License
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//
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// Licensed to the Apache Software Foundation (ASF) under one or more
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// contributor license agreements. See the NOTICE file distributed with
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// this work for additional information regarding copyright ownership.
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// The ASF licenses this file to you under the Apache License, Version 2.0
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// (the "License"); you may not use this file except in compliance with
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// the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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#endregion
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using System;
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using System.Collections;
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using log4net.Repository;
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namespace log4net.Core
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{
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#region WrapperCreationHandler
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/// <summary>
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/// Delegate used to handle creation of new wrappers.
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/// </summary>
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/// <param name="logger">The logger to wrap in a wrapper.</param>
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/// <remarks>
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/// <para>
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/// Delegate used to handle creation of new wrappers. This delegate
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/// is called from the <see cref="WrapperMap.CreateNewWrapperObject"/>
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/// method to construct the wrapper for the specified logger.
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/// </para>
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/// <para>
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/// The delegate to use is supplied to the <see cref="WrapperMap"/>
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/// constructor.
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/// </para>
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/// </remarks>
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public delegate ILoggerWrapper WrapperCreationHandler(ILogger logger);
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#endregion WrapperCreationHandler
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/// <summary>
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/// Maps between logger objects and wrapper objects.
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/// </summary>
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/// <remarks>
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/// <para>
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/// This class maintains a mapping between <see cref="ILogger"/> objects and
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/// <see cref="ILoggerWrapper"/> objects. Use the <see cref="GetWrapper"/> method to
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/// lookup the <see cref="ILoggerWrapper"/> for the specified <see cref="ILogger"/>.
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/// </para>
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/// <para>
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/// New wrapper instances are created by the <see cref="CreateNewWrapperObject"/>
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/// method. The default behavior is for this method to delegate construction
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/// of the wrapper to the <see cref="WrapperCreationHandler"/> delegate supplied
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/// to the constructor. This allows specialization of the behavior without
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/// requiring subclassing of this type.
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/// </para>
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/// </remarks>
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/// <author>Nicko Cadell</author>
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/// <author>Gert Driesen</author>
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public class WrapperMap
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{
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#region Public Instance Constructors
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/// <summary>
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/// Initializes a new instance of the <see cref="WrapperMap" />
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/// </summary>
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/// <param name="createWrapperHandler">The handler to use to create the wrapper objects.</param>
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/// <remarks>
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/// <para>
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/// Initializes a new instance of the <see cref="WrapperMap" /> class with
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/// the specified handler to create the wrapper objects.
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/// </para>
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/// </remarks>
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public WrapperMap(WrapperCreationHandler createWrapperHandler)
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{
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m_createWrapperHandler = createWrapperHandler;
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// Create the delegates for the event callbacks
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m_shutdownHandler = new LoggerRepositoryShutdownEventHandler(ILoggerRepository_Shutdown);
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}
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#endregion Public Instance Constructors
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#region Public Instance Properties
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/// <summary>
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/// Gets the wrapper object for the specified logger.
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/// </summary>
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/// <returns>The wrapper object for the specified logger</returns>
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/// <remarks>
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/// <para>
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/// If the logger is null then the corresponding wrapper is null.
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/// </para>
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/// <para>
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/// Looks up the wrapper it it has previously been requested and
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/// returns it. If the wrapper has never been requested before then
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/// the <see cref="CreateNewWrapperObject"/> virtual method is
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/// called.
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/// </para>
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/// </remarks>
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virtual public ILoggerWrapper GetWrapper(ILogger logger)
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{
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// If the logger is null then the corresponding wrapper is null
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if (logger == null)
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{
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return null;
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}
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lock(this)
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{
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// Lookup hierarchy in map.
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Hashtable wrappersMap = (Hashtable)m_repositories[logger.Repository];
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if (wrappersMap == null)
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{
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// Hierarchy does not exist in map.
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// Must register with hierarchy
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wrappersMap = new Hashtable();
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m_repositories[logger.Repository] = wrappersMap;
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// Register for config reset & shutdown on repository
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logger.Repository.ShutdownEvent += m_shutdownHandler;
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}
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// Look for the wrapper object in the map
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ILoggerWrapper wrapperObject = wrappersMap[logger] as ILoggerWrapper;
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if (wrapperObject == null)
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{
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// No wrapper object exists for the specified logger
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// Create a new wrapper wrapping the logger
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wrapperObject = CreateNewWrapperObject(logger);
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// Store wrapper logger in map
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wrappersMap[logger] = wrapperObject;
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}
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return wrapperObject;
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}
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}
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#endregion Public Instance Properties
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#region Protected Instance Properties
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/// <summary>
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/// Gets the map of logger repositories.
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/// </summary>
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/// <value>
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/// Map of logger repositories.
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/// </value>
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/// <remarks>
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/// <para>
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/// Gets the hashtable that is keyed on <see cref="ILoggerRepository"/>. The
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/// values are hashtables keyed on <see cref="ILogger"/> with the
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/// value being the corresponding <see cref="ILoggerWrapper"/>.
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/// </para>
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/// </remarks>
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protected Hashtable Repositories
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{
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get { return this.m_repositories; }
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}
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#endregion Protected Instance Properties
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#region Protected Instance Methods
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/// <summary>
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/// Creates the wrapper object for the specified logger.
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/// </summary>
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/// <param name="logger">The logger to wrap in a wrapper.</param>
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/// <returns>The wrapper object for the logger.</returns>
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/// <remarks>
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/// <para>
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/// This implementation uses the <see cref="WrapperCreationHandler"/>
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/// passed to the constructor to create the wrapper. This method
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/// can be overridden in a subclass.
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/// </para>
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/// </remarks>
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virtual protected ILoggerWrapper CreateNewWrapperObject(ILogger logger)
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{
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if (m_createWrapperHandler != null)
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{
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return m_createWrapperHandler(logger);
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}
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return null;
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}
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/// <summary>
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/// Called when a monitored repository shutdown event is received.
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/// </summary>
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/// <param name="repository">The <see cref="ILoggerRepository"/> that is shutting down</param>
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/// <remarks>
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/// <para>
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/// This method is called when a <see cref="ILoggerRepository"/> that this
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/// <see cref="WrapperMap"/> is holding loggers for has signaled its shutdown
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/// event <see cref="ILoggerRepository.ShutdownEvent"/>. The default
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/// behavior of this method is to release the references to the loggers
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/// and their wrappers generated for this repository.
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/// </para>
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/// </remarks>
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virtual protected void RepositoryShutdown(ILoggerRepository repository)
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{
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lock(this)
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{
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// Remove the repository from map
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m_repositories.Remove(repository);
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// Unhook events from the repository
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repository.ShutdownEvent -= m_shutdownHandler;
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}
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}
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/// <summary>
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/// Event handler for repository shutdown event.
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/// </summary>
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/// <param name="sender">The sender of the event.</param>
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/// <param name="e">The event args.</param>
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private void ILoggerRepository_Shutdown(object sender, EventArgs e)
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{
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ILoggerRepository repository = sender as ILoggerRepository;
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if (repository != null)
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{
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// Remove all repository from map
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RepositoryShutdown(repository);
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}
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}
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#endregion Protected Instance Methods
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#region Private Instance Variables
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/// <summary>
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/// Map of logger repositories to hashtables of ILogger to ILoggerWrapper mappings
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/// </summary>
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private readonly Hashtable m_repositories = new Hashtable();
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/// <summary>
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/// The handler to use to create the extension wrapper objects.
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/// </summary>
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private readonly WrapperCreationHandler m_createWrapperHandler;
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/// <summary>
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/// Internal reference to the delegate used to register for repository shutdown events.
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/// </summary>
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private readonly LoggerRepositoryShutdownEventHandler m_shutdownHandler;
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#endregion Private Instance Variables
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}
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}
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