Process Monitor is an advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity. You can get more information here
A couple of months ago, I ran into a very strange issue with some data update functionality involving two separate but related applications, one a WPF client and the other a console application running as a scheduled task.
The data update happened in two ways. In the first case, the user explicitly requested for an update using one of the context menu options inside the WPF Client. In the second case, the data update request was automatically queued up by the same Client when certain state changes happened. These queued requests were then processed by the scheduled console application at a later time.The code to perform the actual data update was in a separate dll and both these applications were referencing the same dll.
What was strange was that the manual request was updating the data successfully whereas the queued up request was failing to do so.
I stepped through the code but I was not able to find anything different. so I decided to use the process monitor to troubleshoot this issue. I ran procmon and monitored the manual data update request. Procmon shows you all the activities like registry access and files being loaded. I didn't notice any assembly loading failures or any other access failures.
I then repeated the same process with the console process. In this case, I noticed that there was an assembly loading failure. The console process was trying to load a particular assembly and it wasn't able to locate it after trying several locations. Procmon shows you all the paths that the process is looking at. The assembly that the process was trying to load was missing and that was the reason for the data update failure. Once we dropped the missing dll into a specific location, the process was able to load it and the data process worked just fine.
We later found out that the install team had forgotten to include that particular dll while building their installers. Once the installer got fixed, the data update issue went away.
