NLog.Web: Is there a way to get rid of Object Reference exception for ${aspnet-sessionid} in internal logs for .net core 2. In case logger is being called in layer without HttpContext in it

Hi All!

Issue Template Info:

Type (choose one): - Question My question is there a way to write when clause or other clause in layout to exclude the exception throwing from internal-logs in case HttpContext is not determined in the layer?

It extremely hardens troubleshooting from internal nlog logs.

NLog version: Resolved as 4.6.3

NLog.Web/NLog.Web.AspNetCore version: <PackageReference Include="NLog.Web.AspNetCore" Version="4.8.2" />

NLog.Extensions.Logging version: Resolved as 1.5.0 from NLog.Web.AspNetCore.

Platform: .NET Core 2

Current NLog config (xml or C#, if relevant)

<configuration>
  <configSection>
    <section name="nlog" type="NLog.NLogConfig.ConfigSectionHandler,NLog"/>
  </configSection>
  <nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" autoReload="true" internalLogLevel="info" internalLogFile="internal-nlog.txt">
    <extensions>
      <add assemblyFile="Microsoft.ApplicationInsights.NLogTarget.dll" />
    </extensions>
    <targets async="true">
      
      <target name="dbTarget" xsi:type="Database" 
              connectionString="YourConnectionString" 
              keepConnection="true" 
              commandText="YourSchema.SaveLogEvent 
                @timeStamp,
                @level, 
                @username, 
                @logger, 
                @url, 
                @machineName,
                @threadId,
                @sessionId,
                @referrer,
                @userAgent,
                @code,
                @message">
        <parameter name="@timeStamp" layout="${date}" />
        <parameter name="@level" layout="${level}" />
        <parameter name="@username" layout="${aspnet-user-identity}" />
        <parameter name="@logger" layout="${logger}" />
        <parameter name="@url" layout="${aspnet-request-url:IncludeHost=true:IncludePort=true:IncludeQueryString=true:IncludeScheme=true}" />
        <parameter name="@machineName" layout="${machinename}" />
        <parameter name="@threadId" layout="${threadid}" />
        <parameter name="@sessionId" layout="${aspnet-sessionid}" />
        <parameter name="@referrer" layout="${aspnet-request-referrer}" />
        <parameter name="@userAgent" layout="${aspnet-request-useragent}" />
        <parameter name="@code" layout="${event-context:item=Code}" />
        <parameter name="@message" layout="${message}" />
      </target>
   
      <target xsi:type="ApplicationInsightsTarget" name="aiTarget" instrumentationKey="YourInstrumentationKey">
        <layout xsi:type="JsonLayout" includeAllProperties="true">
          <attribute name="exception" layout="${exception}" />
          <attribute name="threadId" layout="${threadid}" />
          <attribute name="username" layout="${aspnet-user-identity}" />
          <attribute name="url" layout="${aspnet-request-url:IncludeHost=true:IncludePort=true:IncludeQueryString=true:IncludeScheme=true}" />
          <attribute name="severity" layout="${level:lowercase=true}" />
          <attribute name="eventProperties" >
            <layout type='JsonLayout' includeAllProperties="true"  maxRecursionLimit="5"/>
          </attribute>
        </layout>
      </target>
    </targets>

    <rules>
      <logger name="*" minlevel="Trace" writeTo="dbTarget" />
       <logger name="*" minlevel="Trace" writeTo="aiTarget" /> 
    </rules>
  </nlog>
</configuration>

Question:

Please check the section after the questions for more information.

• What is the current result? In internal logs i get the exception Object Reference not set for an instance of an object. The transaction to db however comes just with empty session. (which is expected result)
• What is the expected result? Some kind of workaround which will check
• Did you checked the Internal log? Yes.
• Please post full exception details (message, stacktrace, inner exceptions) Message: Object Reference not set for an instance of an object. Details: Is failing inside of the internal log file when trying to call with above layout in the layer where HttpContext is not available. Specifically it fails on ${aspnet-sessionid} retrieving.
• Are there any workarounds? yes/no It doesn’t log the
• Is there a version in which it did work? Didn’t check.
• Can you help us by writing an unit test? I might help.

Additional Information

I use the wrapper class to log the data in the database, obviously for some of the layers aspnet-sessionid will not be available, is there a workaround to check context in layout if it is null to display empty value/or friendly message for logs, else display session Id. It happens on the Db target I use.

I really appreciate help as want o get rid of the Object reference is not set as an instance of a object exception in internal nlog logs.

The common wrapper class will throw the exception when you have a Data Access Layer and you call logger in it as it doesn’t have a clue about HttpContext.

Possibly related question #153