Fusion Log Files are your friend

Firstly this is a very handy tool that a lot of people are unaware of I certainly was, wish I had known about this when trying to fix ClickOnce issues a few years back.

Today I ran into an issue where a small windows forms application was throwing weird exceptions upon start-up, I also had the misfortune of Nuget.exe throwing a tantrum and a colleague asked me had I tried using the Fusion log viewer.

I had a vague idea what it was and remember seeing that mentioned in the event viewer error logs before, but didn’t know much more about it.

The following is how to go about enabling logging for when Visual Studio starts throwing weird errors upon loading up an application.

  1. First of all click Start, and then type in Fusion Log Viewer into the run box, and then right-click on it and run it as an Administrator.


  2. This will bring up the following:-

  3. Click settings and here we enable logging and give it a directory path to save the files to.
    Note that the folder needs to be created first, before it will let you give a path:-

  4. Run the offending app-add in and the log files will be write to the folder you specified.
  5. Upon investigation of these files they usually have a file per missing or wrong assembly, they give you some insight into whats missing as well as the correct version number the code requires.
  • For more info check out Scott Hanselman’s post on this here
  • Let me know if this helps you or any questions then please add a comment.