I've been fiddling with Azure Diagnostics of late, and although the purpose of the following line of code is reasonably clear, the set of valid values that I can use in place of Application!* isn't (taken from here).
diagnosticConfiguration.WindowsEventLog.DataSources.Add("Application!*");
What's the syntax for that string, and specifically... what does the exclamation mark mean?! :)
This is the standard Windows Event Log query. You can get more information here. And some explanation about Azure diagnostics in particular here.
In summary - Application!* will get all entries in the Application event log. But you can limit this by being more specific - for example if you would like events from only particular source, or event event type.