#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.IO;
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using log4net.Util;
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namespace log4net.ObjectRenderer
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{
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/// <summary>
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/// Map class objects to an <see cref="IObjectRenderer"/>.
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/// </summary>
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/// <remarks>
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/// <para>
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/// Maintains a mapping between types that require special
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/// rendering and the <see cref="IObjectRenderer"/> that
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/// is used to render them.
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/// </para>
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/// <para>
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/// The <see cref="FindAndRender(object)"/> method is used to render an
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/// <c>object</c> using the appropriate renderers defined in this map.
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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 RendererMap
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{
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private readonly static Type declaringType = typeof(RendererMap);
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#region Member Variables
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private System.Collections.Hashtable m_map;
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private System.Collections.Hashtable m_cache = new System.Collections.Hashtable();
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private static IObjectRenderer s_defaultRenderer = new DefaultRenderer();
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#endregion
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#region Constructors
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/// <summary>
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/// Default Constructor
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/// </summary>
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/// <remarks>
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/// <para>
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/// Default constructor.
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/// </para>
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/// </remarks>
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public RendererMap()
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{
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m_map = System.Collections.Hashtable.Synchronized(new System.Collections.Hashtable());
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}
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#endregion
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/// <summary>
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/// Render <paramref name="obj"/> using the appropriate renderer.
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/// </summary>
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/// <param name="obj">the object to render to a string</param>
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/// <returns>the object rendered as a string</returns>
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/// <remarks>
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/// <para>
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/// This is a convenience method used to render an object to a string.
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/// The alternative method <see cref="FindAndRender(object,TextWriter)"/>
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/// should be used when streaming output to a <see cref="TextWriter"/>.
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/// </para>
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/// </remarks>
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public string FindAndRender(object obj)
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{
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// Optimisation for strings
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string strData = obj as String;
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if (strData != null)
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{
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return strData;
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}
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StringWriter stringWriter = new StringWriter(System.Globalization.CultureInfo.InvariantCulture);
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FindAndRender(obj, stringWriter);
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return stringWriter.ToString();
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}
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/// <summary>
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/// Render <paramref name="obj"/> using the appropriate renderer.
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/// </summary>
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/// <param name="obj">the object to render to a string</param>
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/// <param name="writer">The writer to render to</param>
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/// <remarks>
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/// <para>
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/// Find the appropriate renderer for the type of the
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/// <paramref name="obj"/> parameter. This is accomplished by calling the
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/// <see cref="Get(Type)"/> method. Once a renderer is found, it is
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/// applied on the object <paramref name="obj"/> and the result is returned
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/// as a <see cref="string"/>.
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/// </para>
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/// </remarks>
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public void FindAndRender(object obj, TextWriter writer)
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{
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if (obj == null)
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{
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writer.Write(SystemInfo.NullText);
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}
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else
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{
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// Optimisation for strings
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string str = obj as string;
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if (str != null)
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{
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writer.Write(str);
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}
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else
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{
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// Lookup the renderer for the specific type
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try
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{
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Get(obj.GetType()).RenderObject(this, obj, writer);
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}
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catch(Exception ex)
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{
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// Exception rendering the object
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log4net.Util.LogLog.Error(declaringType, "Exception while rendering object of type ["+obj.GetType().FullName+"]", ex);
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// return default message
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string objectTypeName = "";
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if (obj != null && obj.GetType() != null)
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{
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objectTypeName = obj.GetType().FullName;
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}
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writer.Write("<log4net.Error>Exception rendering object type ["+objectTypeName+"]");
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if (ex != null)
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{
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string exceptionText = null;
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try
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{
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exceptionText = ex.ToString();
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}
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catch
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{
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// Ignore exception
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}
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writer.Write("<stackTrace>" + exceptionText + "</stackTrace>");
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}
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writer.Write("</log4net.Error>");
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}
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}
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}
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}
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/// <summary>
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/// Gets the renderer for the specified object type
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/// </summary>
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/// <param name="obj">the object to lookup the renderer for</param>
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/// <returns>the renderer for <paramref name="obj"/></returns>
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/// <remarks>
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/// <param>
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/// Gets the renderer for the specified object type.
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/// </param>
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/// <param>
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/// Syntactic sugar method that calls <see cref="Get(Type)"/>
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/// with the type of the object parameter.
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/// </param>
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/// </remarks>
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public IObjectRenderer Get(Object obj)
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{
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if (obj == null)
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{
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return null;
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}
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else
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{
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return Get(obj.GetType());
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}
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}
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/// <summary>
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/// Gets the renderer for the specified type
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/// </summary>
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/// <param name="type">the type to lookup the renderer for</param>
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/// <returns>the renderer for the specified type</returns>
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/// <remarks>
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/// <para>
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/// Returns the renderer for the specified type.
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/// If no specific renderer has been defined the
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/// <see cref="DefaultRenderer"/> will be returned.
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/// </para>
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/// </remarks>
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public IObjectRenderer Get(Type type)
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{
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if (type == null)
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{
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throw new ArgumentNullException("type");
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}
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IObjectRenderer result = null;
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// Check cache
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result = (IObjectRenderer)m_cache[type];
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if (result == null)
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{
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for(Type cur = type; cur != null; cur = cur.BaseType)
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{
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// Search the type's interfaces
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result = SearchTypeAndInterfaces(cur);
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if (result != null)
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{
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break;
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}
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}
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// if not set then use the default renderer
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if (result == null)
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{
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result = s_defaultRenderer;
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}
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// Add to cache
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m_cache[type] = result;
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}
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return result;
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}
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/// <summary>
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/// Internal function to recursively search interfaces
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/// </summary>
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/// <param name="type">the type to lookup the renderer for</param>
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/// <returns>the renderer for the specified type</returns>
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private IObjectRenderer SearchTypeAndInterfaces(Type type)
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{
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IObjectRenderer r = (IObjectRenderer)m_map[type];
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if (r != null)
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{
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return r;
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}
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else
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{
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foreach(Type t in type.GetInterfaces())
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{
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r = SearchTypeAndInterfaces(t);
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if (r != null)
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{
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return r;
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}
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}
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}
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return null;
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}
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/// <summary>
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/// Get the default renderer instance
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/// </summary>
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/// <value>the default renderer</value>
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/// <remarks>
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/// <para>
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/// Get the default renderer
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/// </para>
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/// </remarks>
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public IObjectRenderer DefaultRenderer
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{
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get { return s_defaultRenderer; }
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}
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/// <summary>
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/// Clear the map of renderers
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/// </summary>
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/// <remarks>
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/// <para>
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/// Clear the custom renderers defined by using
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/// <see cref="Put"/>. The <see cref="DefaultRenderer"/>
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/// cannot be removed.
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/// </para>
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/// </remarks>
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public void Clear()
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{
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m_map.Clear();
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m_cache.Clear();
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}
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/// <summary>
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/// Register an <see cref="IObjectRenderer"/> for <paramref name="typeToRender"/>.
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/// </summary>
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/// <param name="typeToRender">the type that will be rendered by <paramref name="renderer"/></param>
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/// <param name="renderer">the renderer for <paramref name="typeToRender"/></param>
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/// <remarks>
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/// <para>
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/// Register an object renderer for a specific source type.
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/// This renderer will be returned from a call to <see cref="Get(Type)"/>
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/// specifying the same <paramref name="typeToRender"/> as an argument.
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/// </para>
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/// </remarks>
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public void Put(Type typeToRender, IObjectRenderer renderer)
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{
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m_cache.Clear();
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if (typeToRender == null)
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{
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throw new ArgumentNullException("typeToRender");
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}
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if (renderer == null)
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{
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throw new ArgumentNullException("renderer");
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}
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m_map[typeToRender] = renderer;
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}
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}
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}
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