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