C# 4 and .NET 4

478 ❘ ChaPTer 19 instrumentAtiOn
(continued)
eVenTlog members
Source
CreateEventSource()
DeleteEventSource()
SourceExists()
WriteEntry()
WriteEvent()
Clear()
Delete()
desCriPTion
The Source property specifi es the source of the event entries to write.
The CreateEventSource() creates a new event source and a new log fi le, if a
new log fi le is specifi ed with this method.
To get rid of an event source, you can invoke DeleteEventSource().
Before creating an event source, you can verify if the source already exists by
using this element.
Write event log entries with either the WriteEntry() or WriteEvent()
method. WriteEntry() is simpler, because you just need to pass a string.
WriteEvent() is more fl exible, because you can use message fi les that are
independent of the application and that support localization.
The Clear() method removes all entries from an event log.
The Delete() method deletes a complete event log.
Creating an event source
Before writing events, you must create an event source. You can use either the CreateEventSource()
method of the EventLog class or the class EventLogInstaller . Because you need administrative privileges
when creating an event source, an installation program would be best for defi ning the new source.
Chapter 17, “Deployment,” explains how to create installation programs.
The following sample verifi es that an event log source named EventLogDemoApp already exists. If it
doesn ’ t exist, an object of type EventSourceCreationData is instantiated that defi nes the source name
EventLogDemoApp and the log name ProCSharpLog . Here, all events of this source are written to the
ProCSharpLog event log. The default is the application log.
string logName = "ProCSharpLog";
string sourceName = "EventLogDemoApp";
if (!EventLog.SourceExists(sourceName))
{
var eventSourceData = new EventSourceCreationData(sourceName,
logName);
}
EventLog.CreateEventSource(eventSourceData);
code snippet EventLogDemo/Program.cs
The name of the event source is an identifi er of the application that writes the events. For the system
administrator reading the log, the information helps in identifying the event log entries to map them to
application categories. Examples of names for event log sources are LoadPerf for the performance monitor,
MSSQLSERVER for Microsoft SQL Server, MsiInstaller for the Windows Installer, Winlogon , Tcpip ,
Time - Service , and so on.
Setting the name Application for the event log writes event log entries to the application log. You can also
create your own log by specifying a different application log name. Log fi les are located in the directory
< windows > \System32\WinEvt\Logs .
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