log4net 1.2.11.0
I am trying to get anything that will allow me to log with a unique value for each ASP.NET request.
I tried %thread, but threads appear to
.asmx files will still call Application_BeginRequest event where you can store your unique GUID in HttpContext.Current.Items (using this collection avoid the odd problem when the request processing jumps threads). Only if you were using WCF (and also then it depends on configuration) this would not work.
If you would like not to touch the application itself, you can use HttpContext.Current.Timestamp that returns the time when the request processing started. Join that with your existing approach of getting the ID of the thread and you will get a unique value.