log4net filter - how to write AND filter to ignore log messages

Question

I am struggling to write an AND conditional filter in log4net. Had it been nLog, I could have written it this way:

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Answer 1

You can create custom filter for your business needs:

public class UserRequestFilter : FilterSkeleton
{
    public override FilterDecision Decide(LoggingEvent loggingEvent)
    {
        if (loggingEvent == null)
            throw new ArgumentNullException("loggingEvent");

        string userId = (string)loggingEvent.Properties["UserId"];
        string url = (string)loggingEvent.Properties["Url"];

        if (String.IsNullOrEmpty(UserId) || String.IsNullOrEmpty(Url))
            return FilterDecision.Neutral;

        if (UserId.Equals(userId) && Url.Equals(url, StringComparison.CurrentCultureIgnoreCase))
            return AcceptOnMatch ? FilterDecision.Accept : FilterDecision.Deny;

        return FilterDecision.Neutral;
    }

    public bool AcceptOnMatch { get; set; }
    public string UserId { get; set; }
    public string Url { get; set; }
}

Configuration will look like this:

Also you can create compound filter, but I didn't find way to use it in configuration. Looks like it could be attached only programmatically (which is useless ^_^):

IAppenderAttachable logger = (IAppenderAttachable)_log.Logger;
AppenderSkeleton appender = (AppenderSkeleton)logger.GetAppender("appenderName");
CompoundFilter compoundFilter = new CompoundFilter();
compoundFilter.AddFilter(new PropertyFilter() { Key = "UserId", StringToMatch = "TEST" });
compoundFilter.AddFilter(new PropertyFilter() { Key = "Url", StringToMatch = @"/foo/foobar.aspx" });
appender.AddFilter(compoundFilter);
logger.AddAppender(appender);

[UPDATE]

Here is trick that you can use - create filter, which will check all filters down the filters chain:

public class DenyAllSubsequentFilter : FilterSkeleton
{
    public override FilterDecision Decide(LoggingEvent loggingEvent)
    {
        IFilter nextFilter = Next;
        if (nextFilter == null)
            return FilterDecision.Accept;

        while (nextFilter != null)
        {
            if (nextFilter.Decide(loggingEvent) != FilterDecision.Deny)
                return FilterDecision.Accept;

            nextFilter = nextFilter.Next;
        }

        return FilterDecision.Deny;
    }
}

Usage:

This filter will deny logging message if all subsequent filters will deny it.