#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 log4net.Core;
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namespace log4net.Filter
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{
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/// <summary>
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/// Implement this interface to provide customized logging event filtering
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/// </summary>
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/// <remarks>
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/// <para>
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/// Users should implement this interface to implement customized logging
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/// event filtering. Note that <see cref="log4net.Repository.Hierarchy.Logger"/> and
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/// <see cref="log4net.Appender.AppenderSkeleton"/>, the parent class of all standard
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/// appenders, have built-in filtering rules. It is suggested that you
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/// first use and understand the built-in rules before rushing to write
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/// your own custom filters.
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/// </para>
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/// <para>
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/// This abstract class assumes and also imposes that filters be
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/// organized in a linear chain. The <see cref="Decide"/>
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/// method of each filter is called sequentially, in the order of their
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/// addition to the chain.
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/// </para>
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/// <para>
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/// The <see cref="Decide"/> method must return one
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/// of the integer constants <see cref="FilterDecision.Deny"/>,
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/// <see cref="FilterDecision.Neutral"/> or <see cref="FilterDecision.Accept"/>.
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/// </para>
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/// <para>
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/// If the value <see cref="FilterDecision.Deny"/> is returned, then the log event is dropped
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/// immediately without consulting with the remaining filters.
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/// </para>
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/// <para>
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/// If the value <see cref="FilterDecision.Neutral"/> is returned, then the next filter
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/// in the chain is consulted. If there are no more filters in the
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/// chain, then the log event is logged. Thus, in the presence of no
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/// filters, the default behavior is to log all logging events.
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/// </para>
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/// <para>
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/// If the value <see cref="FilterDecision.Accept"/> is returned, then the log
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/// event is logged without consulting the remaining filters.
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/// </para>
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/// <para>
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/// The philosophy of log4net filters is largely inspired from the
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/// Linux ipchains.
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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 interface IFilter : IOptionHandler
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{
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/// <summary>
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/// Decide if the logging event should be logged through an appender.
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/// </summary>
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/// <param name="loggingEvent">The LoggingEvent to decide upon</param>
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/// <returns>The decision of the filter</returns>
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/// <remarks>
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/// <para>
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/// If the decision is <see cref="FilterDecision.Deny"/>, then the event will be
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/// dropped. If the decision is <see cref="FilterDecision.Neutral"/>, then the next
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/// filter, if any, will be invoked. If the decision is <see cref="FilterDecision.Accept"/> then
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/// the event will be logged without consulting with other filters in
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/// the chain.
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/// </para>
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/// </remarks>
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FilterDecision Decide(LoggingEvent loggingEvent);
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/// <summary>
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/// Property to get and set the next filter
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/// </summary>
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/// <value>
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/// The next filter in the chain
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/// </value>
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/// <remarks>
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/// <para>
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/// Filters are typically composed into chains. This property allows the next filter in
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/// the chain to be accessed.
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/// </para>
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/// </remarks>
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IFilter Next { get; set; }
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}
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}
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