src/log4net/Appender/AspNetTraceAppender.cs

#if NET462_OR_GREATER
#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.Web;

using log4net.Layout;
using log4net.Core;

namespace log4net.Appender
{
  /// <summary>
  /// <para>
  /// Appends log events to the ASP.NET <see cref="TraceContext"/> system.
  /// </para>
  /// </summary>
  /// <remarks>
  /// <para>
  /// Diagnostic information and tracing messages that you specify are appended to the output 
  /// of the page that is sent to the requesting browser. Optionally, you can view this information
  /// from a separate trace viewer (Trace.axd) that displays trace information for every page in a 
  /// given application.
  /// </para>
  /// <para>
  /// Trace statements are processed and displayed only when tracing is enabled. You can control 
  /// whether tracing is displayed to a page, to the trace viewer, or both.
  /// </para>
  /// <para>
  /// The logging event is passed to the <see cref="M:TraceContext.Write(string)"/> or 
  /// <see cref="M:TraceContext.Warn(string)"/> method depending on the level of the logging event.
  /// The event's logger name is the default value for the category parameter of the Write/Warn method. 
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  /// <author>Gert Driesen</author>
  /// <author>Ron Grabowski</author>
  public class AspNetTraceAppender : AppenderSkeleton 
  {
    #region Public Instances Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="AspNetTraceAppender" /> class.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Default constructor.
    /// </para>
    /// </remarks>
    public AspNetTraceAppender()
    {
    }

    #endregion // Public Instances Constructors

    #region Override implementation of AppenderSkeleton

    /// <summary>
    /// Write the logging event to the ASP.NET trace
    /// </summary>
    /// <param name="loggingEvent">the event to log</param>
    /// <remarks>
    /// <para>
    /// Write the logging event to the ASP.NET trace
    /// <c>HttpContext.Current.Trace</c> 
    /// (<see cref="TraceContext"/>).
    /// </para>
    /// </remarks>
    protected override void Append(LoggingEvent loggingEvent) 
    {
      // check if log4net is running in the context of an ASP.NET application
      if (HttpContext.Current != null) 
      {
        // check if tracing is enabled for the current context
        if (HttpContext.Current.Trace.IsEnabled) 
        {
          if (loggingEvent.Level >= Level.Warn) 
          {
            HttpContext.Current.Trace.Warn(m_category.Format(loggingEvent), RenderLoggingEvent(loggingEvent));
          }
          else 
          {
            HttpContext.Current.Trace.Write(m_category.Format(loggingEvent), RenderLoggingEvent(loggingEvent));
          }
        }
      }
    }

    /// <summary>
    /// This appender requires a <see cref="Layout"/> to be set.
    /// </summary>
    /// <value><c>true</c></value>
    /// <remarks>
    /// <para>
    /// This appender requires a <see cref="Layout"/> to be set.
    /// </para>
    /// </remarks>
    protected override bool RequiresLayout
    {
      get { return true; }
    }

    #endregion // Override implementation of AppenderSkeleton

    #region Public Instance Properties

    /// <summary>
    /// The category parameter sent to the Trace method.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Defaults to %logger which will use the logger name of the current 
    /// <see cref="LoggingEvent"/> as the category parameter.
    /// </para>
    /// <para>
    /// </para> 
    /// </remarks>
    public PatternLayout Category
    {
      get { return m_category; }
      set { m_category = value; }
    }

    #endregion

    #region Private Instance Fields

    /// <summary>
    /// Defaults to %logger
    /// </summary>
    private PatternLayout m_category = new PatternLayout("%logger");

    #endregion
  }
}
#endif