The event source indicates what logs the event. It is often the name of the application, or the name of a component within a large application.

The installer uses the value of the EventLogInstaller.Source property to register your application with the event log as a valid source of entries. A new source name cannot match an existing source name or an existing event log name. Each source can only write to one event log at a time; however, your application can use multiple sources to write to multiple event logs. For example, your application might require multiple sources configured for different event logs or different resource files.

Applications and services should write to the Application log or a custom log. Device drivers should write to the System log. If you do not specify a log name before the installer runs, the installer registers your source to the Application log. If you specify the name of a log that does not exist, the system registers the EventLogInstaller.Source to that log, but the log is not created until the first entry is written to it.

Use System.Diagnostics.EventLogInstaller to register a new source for a new or existing event log; do not use System.Diagnostics.EventLogInstaller to change an existing source. The System.Diagnostics.EventLogInstaller class does not modify the configuration properties of an existing source to match the specified installation properties. The EventLogInstaller.Install(IDictionary) method throws an exception if the EventLogInstaller.Source property matches a source name that is registered for a different event log on the computer. The EventLogInstaller.Install(IDictionary) method does not register the source if the EventLogInstaller.Source property matches a source name that is already registered for the same event log specified in the EventLogInstaller.Log property.

For more detailed information about the behaviors of event logs and sources, see the System.Diagnostics.EventLog class documentation for the EventLog.Log and EventLog.Source properties.