Proposed bug fix for AspNetRequestPatternConverter.Convert()

[George Chung]

Hello,
I'm new to this mailing list. Sorry if this is not the appropriate way to
report a bug fix. Dereferencing HttpContext.Request will throw an exception
if you call it in an Asp.net application's Application_Start().

Thus, if you have log4net logging *and* you use a pattern layout format
like %aspnet-request{REMOTE_ADDR} *and* you call Log4net inside
Application_Start(), Log4net will throw an exception trying to log the
message. The stack will look like this:

log4net:ERROR [RollingFileAppender] ErrorCode: GenericFailure. Failed in
DoAppend
System.Web.HttpException (0x80004005): Request is not available in this
context
   at System.Web.HttpContext.get_Request()
   at
log4net.Layout.Pattern.AspNetRequestPatternConverter.Convert(TextWriter
writer, LoggingEvent loggingEvent, HttpContext httpContext)
   at
log4net.Layout.Pattern.AspNetPatternLayoutConverter.Convert(TextWriter
writer, LoggingEvent loggingEvent)
   at log4net.Layout.Pattern.PatternLayoutConverter.Convert(TextWriter
writer, Object state)
   at log4net.Util.PatternConverter.Format(TextWriter writer, Object state)
   at log4net.Layout.PatternLayout.Format(TextWriter writer, LoggingEvent
loggingEvent)
   at log4net.Layout.Layout2RawLayoutAdapter.Format(LoggingEvent
loggingEvent)


Here is my proposed fix:

internal sealed class AspNetRequestPatternConverter :
AspNetPatternLayoutConverter
    {
        /// <summary>
        /// Write the ASP.Net Cache item to the output
        /// </summary>
        /// <param name="writer"><see cref="TextWriter" /> that will
receive the formatted result.</param>
        /// <param name="loggingEvent">The <see cref="LoggingEvent" />
on which the pattern converter should be executed.</param>
        /// <param name="httpContext">The <see cref="HttpContext" />
under which the ASP.Net request is running.</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>
        /// </remarks>
        protected override void Convert(TextWriter writer,
LoggingEvent loggingEvent, HttpContext httpContext)
        {
            bool requestExists = true;

            HttpRequest request = null;
            try
            {
                request = httpContext.Request;
                if (request == null)
                    requestExists = false;
            }
            catch (System.Web.HttpException)
            {
                requestExists = false;
            }

            if (requestExists)
            {
                if (Option != null)
                {
                    WriteObject(writer, loggingEvent.Repository,
request.Params[Option]);
                }
                else
                {
                    WriteObject(writer, loggingEvent.Repository,
request.Params);
                }
            }
            else
            {
                writer.Write(SystemInfo.NotAvailableText);
            }
        }
    }