AppSettings

Serilog supports a simple <appSettings>-based configuration syntax in App.config and Web.config files to set the minimum level, enrich events with additional properties, and control log output.

Serilog is primarily configured using code, with settings support intended as a supplementary feature. It is not comprehensive but most logger configuration tasks can be achieved using it.

Enabling <appSettings> configuration

The <appSettings> support package needs to be installed from NuGet:

Install-Package Serilog.Settings.AppSettings

To read configuration from <appSettings> use the ReadFrom.AppSettings() extension method on your LoggerConfiguration:

Log.Logger = new LoggerConfiguration()
  .ReadFrom.AppSettings()
  ... // Other configuration here, then
  .CreateLogger()

You can mix and match XML and code-based configuration, but each sink must be configured either using XML or in code - sinks added in code can't be modified via app settings.

Configuring the logger

To configure the logger, an <appSettings> element should be included in the program's App.config or Web.config file.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="serilog:minimum-level" value="Verbose" />
    <!-- More settings here -->

Setting the minimum level

To set the logging level for the app use the serilog:minimum-level setting key.

  <add key="serilog:minimum-level" value="Verbose" />

Valid values are those defined in the LogEventLevel enumeration: Verbose, Debug, Information, Warning, Error, Fatal.

Adding a sink

Sinks are added with the serilog:write-to key. The setting name matches the configuration method name that you'd use in code, so the following are equivalent:

  .WriteTo.LiterateConsole()

In XML:

  <add key="serilog:write-to:LiterateConsole" />

NOTE: When using serilog:* keys need to be unique.

Sink assemblies must be specified using the serilog:using syntax. For example, to configure

  <add key="serilog:using:LiterateConsole" value="Serilog.Sinks.Literate" />
  <add key="serilog:write-to:LiterateConsole"/>

If the sink accepts parameters, these are specified by appending the parameter name to the setting.

  .WriteTo.RollingFile(@"C:\Logs\myapp-{Date}.txt", retainedFileCountLimit: 10)

In XML:

  <add key="serilog:using:RollingFile" value="Serilog.Sinks.RollingFile" />
  <add key="serilog:write-to:RollingFile.pathFormat" value="C:\Logs\myapp-{Date}.txt" />
  <add key="serilog:write-to:RollingFile.retainedFileCountLimit" value="10" />

Any environment variables specified in a setting value (e.g. %TEMP%) will be expanded appropriately when read.

Using sink extensions from additional assemblies

To use sinks and enrichers from additional assemblies, specify them with the serilog:using key.

For example, to use configuration from the Serilog.Sinks.EventLog assembly:

  <add key="serilog:using:EventLog" value="Serilog.Sinks.EventLog" />
  <add key="serilog:write-to:EventLog.source" value="Serilog Demo" />

Enriching with properties

To attach additional properties to log events, specify them with the serilog:enrich:with-property directive.

For example, to add the property Release with the value "1.2-develop" to all events:

  <add key="serilog:enrich:with-property:Release" value="1.2-develop" />

Adding minimum level overrides

Since Serilog 2.1, minimum level overrides can be added to change the minimum level for some specific namespaces. This is done with the setting key serilog:minimum-level:override: followed by the source context prefix.

For instance, the following are equivalent :

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Information()
    .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
    .MinimumLevel.Override("Microsoft.AspNetCore.Mvc", LogEventLevel.Error)

and in XML

    <add key="serilog:minimum-level" value="Information" />
    <add key="serilog:minimum-level:override:Microsoft" value="Warning" />
    <add key="serilog:minimum-level:override:Microsoft.AspNetCore.Mvc" value="Error" />