This seems to do the trick if you want to log to the Windows event log:

private void logError(string message, string source)
{
	System.Diagnostics.EventLog log = new System.Diagnostics.EventLog();
	log.Source = source;
	log.WriteEntry(message, System.Diagnostics.EventLogEntryType.Error);
	log.Close();
}

private void logError(Exception exception, string source)
{
	logError(exception.ToString(), source);
}

Put it in your class, or in a special logging class.

Read more:

• http://www.csharpfriends.com/Articles/getArticle.aspx?articleID=77
• http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx
  I might add that the comment about latency when creating event log sources does not seem to apply on Windows 2008 Server (where I tested the above code – which doesn’t even create a source… ummm)
• http://www.codeproject.com/KB/architecture/exceptionbestpractices.aspx