src/log4net/Util/PatternStringConverters/AppSettingPatternConverter.cs

#region Apache License
//
// 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.
//
#endregion

// .NET Compact Framework 1.0 has no support for application .config files
#if !NETCF && NET_2_0

using System;
using System.Text;
using System.IO;
using System.Collections;

using log4net.Core;
using log4net.Util;
using log4net.Repository;

namespace log4net.Util.PatternStringConverters
{
    /// <summary>
    /// AppSetting pattern converter
    /// </summary>
    /// <remarks>
    /// <para>
    /// This pattern converter reads appSettings from the application configuration file.
    /// </para>
    /// <para>
    /// If the <see cref="PatternConverter.Option"/> is specified then that will be used to
    /// lookup a single appSettings value. If no <see cref="PatternConverter.Option"/> is specified
    /// then all appSettings will be dumped as a list of key value pairs.
    /// </para>
    /// <para>
    /// A typical use is to specify a base directory for log files, e.g.
    /// <example>
    /// <![CDATA[
    /// <log4net>
    ///    <appender name="MyAppender" type="log4net.Appender.RollingFileAppender">
    ///      <file type="log4net.Util.PatternString" value="appsetting{LogDirectory}MyApp.log"/>
    ///       ...
    ///   </appender>
    /// </log4net>
    /// ]]>
    /// </example>
    /// </para>
    /// </remarks>
    internal sealed class AppSettingPatternConverter : PatternConverter
    {
        private static IDictionary AppSettingsDictionary
        {
            get
            {
                if (_appSettingsHashTable == null)
                {
                    Hashtable h = new Hashtable();
                    foreach(string key in System.Configuration.ConfigurationManager.AppSettings)
                    {
                        h.Add(key, System.Configuration.ConfigurationManager.AppSettings[key]);
                    }
                    _appSettingsHashTable = h;
                }
                return _appSettingsHashTable;
            }

        }
        private static Hashtable _appSettingsHashTable;

        /// <summary>
        /// Write the property value to the output
        /// </summary>
        /// <param name="writer"><see cref="TextWriter" /> that will receive the formatted result.</param>
        /// <param name="state">null, state is not set</param>
        /// <remarks>
        /// <para>
        /// Writes out the value of a named property. The property name
        /// should be set in the <see cref="log4net.Util.PatternConverter.Option"/>
        /// property.
        /// </para>
        /// <para>
        /// If the <see cref="log4net.Util.PatternConverter.Option"/> is set to <c>null</c>
        /// then all the properties are written as key value pairs.
        /// </para>
        /// </remarks>
        override protected void Convert(TextWriter writer, object state)
        {

            if (Option != null)
            {
                // Write the value for the specified key
                WriteObject(writer, null, System.Configuration.ConfigurationManager.AppSettings[Option]);
            }
            else
            {
                // Write all the key value pairs
                WriteDictionary(writer, null, AppSettingsDictionary);
            }
        }
    }
}
#endif // !NETCF && NET_2_0