Send an Email When an Error Occurs in C# using log4net

Question

Currently my application is using log4net to log errors, the web.config for this is as followed:

<log4net>
    <appender name="FileAppender" type="log4net.Appender.RollingFileAppender">
      <file type="log4net.Util.PatternString" value="../../logs/gateway_%date{yyyyMMdd}.log" />
      <appendToFile value="true" />
      <rollingStyle value="Date" />
      <datePattern value="yyyyMMdd" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] – %message%newline" />
      </layout>
    </appender>
    <root>
      <level value="DEBUG" />
      <appender-ref ref="RollingLogFileAppenderOutput" />
    </root>
  </log4net>

However, the client now wants each error to be emailled to them.

What is the easiest way to do this, can you do it within the web.config file?

Refer this for adding Smtp username password in log4net config https://stackoverflow.com/questions/15523613/log4net-smtp-appender-not-sending-emails — Varun, Jan 08 '19 at 10:18

score 55 · Accepted Answer · edited Jul 01 '22 at 22:47

55

You should use SmtpAppender

<appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">
    <to value="to@example.com" />
    <from value="from@example.com" />
    <subject value="test logging message" />
    <smtpHost value="SMTPServer.example.com" />
    <bufferSize value="512" />
    <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>

<logger name="ErrorLogger">
    <level value="Error" />
    <appender-ref ref="FileAppender" />
</logger>
<logger name="EmailLogger">
    <level value="Error" />
    <appender-ref ref="SmtpAppender" />
</logger>

In order to send emails only for an specific error you could do something like this

try
{
  // your logic
}
catch (MySpecificException ex)
{
   // I only send emails for exception of type MySpecificException
   LogManager.GetLogger("EmailLogger").Error(ex);
}
catch (Exception ex)
{
   // Just log to a file for the rest
   LogManager.GetLogger("ErrorLogger").Error(ex);
}

edited Jul 01 '22 at 22:47

Stephen Ostermiller

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answered Apr 30 '12 at 14:01

Claudio Redi

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you will also need to have access to an smtp server, if you do not have one there are a few good ones available online, just do a google search – pengibot Apr 30 '12 at 14:03
however, this would therefore mean 'every' message is sent correct? Is their a way to only email 'certain' errors? – swade1987 Apr 30 '12 at 14:07
@swade1987: with this configuration you won't send all errors automatically, you'll have to add a code line to log. Since you have to manually log errors, you can decide which errors to log and which not. – Claudio Redi Apr 30 '12 at 14:10
@ClaudioRedi - currently when I log an error I just write "ErrorHandler.LogError(ex, "Gateway - Security - IsNonceSentFromDeviceValid - Failed");" so am I not going to have two types ErrorHandler.LogErrorWithMail() and ErrorHandler.LogError() – swade1987 Apr 30 '12 at 14:25
@swade1987: I can't come up at this moment to anything that would solve your specific problem without changing you logging logic. Let you know if I come up with something. – Claudio Redi Apr 30 '12 at 16:23
I think the first answer of Claudio was OK. It just needs to be combined with either a string match filter (if that is enough) or some custom filter (that can filter on exception type or whatever is necessary). – Stefan Egli May 02 '12 at 17:58
link to smtpappender is 404'ing – user3791372 Oct 17 '16 at 14:20
@user3791372: thanks, removed the link. Will try to find a replace for it – Claudio Redi Oct 17 '16 at 14:28

Send an Email When an Error Occurs in C# using log4net

1 Answers1