#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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namespace log4net.Util
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{
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/// <summary>
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/// This class aggregates several PropertiesDictionary collections together.
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/// </summary>
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/// <remarks>
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/// <para>
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/// Provides a dictionary style lookup over an ordered list of
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/// <see cref="PropertiesDictionary"/> collections.
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/// </para>
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/// </remarks>
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/// <author>Nicko Cadell</author>
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public sealed class CompositeProperties
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{
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#region Private Instance Fields
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private PropertiesDictionary m_flattened = null;
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private ArrayList m_nestedProperties = new ArrayList();
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#endregion Private Instance Fields
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#region Public Instance Constructors
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/// <summary>
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/// Constructor
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/// </summary>
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/// <remarks>
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/// <para>
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/// Initializes a new instance of the <see cref="CompositeProperties" /> class.
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/// </para>
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/// </remarks>
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internal CompositeProperties()
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{
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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 value of a property
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/// </summary>
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/// <value>
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/// The value for the property with the specified key
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/// </value>
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/// <remarks>
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/// <para>
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/// Looks up the value for the <paramref name="key" /> specified.
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/// The <see cref="PropertiesDictionary"/> collections are searched
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/// in the order in which they were added to this collection. The value
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/// returned is the value held by the first collection that contains
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/// the specified key.
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/// </para>
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/// <para>
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/// If none of the collections contain the specified key then
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/// <c>null</c> is returned.
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/// </para>
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/// </remarks>
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public object this[string key]
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{
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get
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{
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// Look in the flattened properties first
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if (m_flattened != null)
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{
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return m_flattened[key];
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}
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// Look for the key in all the nested properties
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foreach(ReadOnlyPropertiesDictionary cur in m_nestedProperties)
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{
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if (cur.Contains(key))
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{
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return cur[key];
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}
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}
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return null;
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}
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}
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#endregion Public Instance Properties
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#region Public Instance Methods
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/// <summary>
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/// Add a Properties Dictionary to this composite collection
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/// </summary>
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/// <param name="properties">the properties to add</param>
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/// <remarks>
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/// <para>
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/// Properties dictionaries added first take precedence over dictionaries added
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/// later.
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/// </para>
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/// </remarks>
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public void Add(ReadOnlyPropertiesDictionary properties)
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{
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m_flattened = null;
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m_nestedProperties.Add(properties);
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}
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/// <summary>
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/// Flatten this composite collection into a single properties dictionary
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/// </summary>
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/// <returns>the flattened dictionary</returns>
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/// <remarks>
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/// <para>
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/// Reduces the collection of ordered dictionaries to a single dictionary
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/// containing the resultant values for the keys.
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/// </para>
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/// </remarks>
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public PropertiesDictionary Flatten()
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{
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if (m_flattened == null)
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{
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m_flattened = new PropertiesDictionary();
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for(int i=m_nestedProperties.Count; --i>=0; )
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{
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ReadOnlyPropertiesDictionary cur = (ReadOnlyPropertiesDictionary)m_nestedProperties[i];
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foreach(DictionaryEntry entry in cur)
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{
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m_flattened[(string)entry.Key] = entry.Value;
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}
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}
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}
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return m_flattened;
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}
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#endregion Public Instance Methods
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}
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}
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