Value from the App Settings configuration (app.config / web.config)

Platforms Supported: Limited (.NET Framework only, when using .NET Core then ${configsetting} can be used to read values from appsettings.json-file)

Introduced with NLog 3.0 and with NLog 4.6+ it was included in default NLog-package without needing NLog.Extended.

${appsetting:item=String:default=String}

• item - Key in the apps setting. Required

  Introduced with NLog v4.5, and replaces the Name-option.

• Default - Default value if not present. Optional.

Example .config

<configuration>
  <appSettings>
    <add key="MyKey" value="MyApplication" />
  </appSettings>
</configuration>

Example renderer: produces MyApplication is this case:

${appsetting:item=MyKey:default=mydefault}

Example#2 renderer: produces mydefault is this case:

${appsetting:item=MyKey2:default=mydefault}

Introduced with NLog 4.6.5

<configuration>
  <appSettings>
    <add key="MyKey" value="MyApplication" />
  </appSettings>
  <connectionStrings>
    <add name="ElasticUrl" connectionString="http://localhost:9200"/>
  </connectionStrings>
</configuration>

Example#3 renderer: produces http://localhost:9200 is this case:

${appsetting:item=connectionStrings.ElasticUrl}

Note remember to uninstall/remove NLog.Extended-nuget-package from the application when having upgraded to NLog v4.6.5, else connectionStrings-lookup will not work.