How can I specify a layout and conversionPattern for the resulting emails subject?
The BufferSize will need to be less than or equal to 1 so no buffering will occur.
The CodeProject article log4net NonBufferedSmtpAppenderWithSubjectLayout looks promising.
By inheriting from the required base appender (SmtpPickupDirAppender in my case) and adding a ILayout property it is possible to change the Subject in the Append method.
public class SmtpSubjectLayoutPickupDirAppender : log4net.Appender.SmtpPickupDirAppender
{
public SmtpSubjectLayoutPickupDirAppender()
: base()
{
}
public ILayout SubjectLayout
{
get;
set;
}
protected override void Append(log4net.Core.LoggingEvent loggingEvent)
{
if (this.BufferSize <= 1 && this.SubjectLayout != null)
{
StringWriter subjectWriter = new StringWriter(System.Globalization.CultureInfo.InvariantCulture);
this.SubjectLayout.Format(subjectWriter, loggingEvent);
this.Subject = subjectWriter.ToString();
}
base.Append(loggingEvent);
}
}
This can then be configured by specifying a subjectLayout property to override the default subject.
<appender name="SmtpPickupDirAppender" type="namespace.for.SmtpSubjectLayoutPickupDirAppender">
<to value="[email protected]" />
<from value="[email protected]" />
<subject value="test logging message" />
<subjectLayout type="log4net.Layout.PatternLayout, log4net">
<conversionPattern value="Logging message - %message"/>
</subjectLayout>
<pickupDir value="C:\SmtpPickup" />
<bufferSize value="1" />
<lossy value="true" />
<evaluator type="log4net.Core.LevelEvaluator">
<threshold value="WARN"/>
</evaluator>
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%newline%date [%thread] %-5level %logger [%property{NDC}] - %message%newline%newline%newline" />
</layout>
</appender>