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Troubleshooting Basics # 1 : Fusion

Posted by Ankush on January 26, 2011

Have you ever come across such a scenario where  .NET assembly is not getting loaded for some reason or it is getting loaded but not showing up the latest things which you added in the assembly. For some reason, it still loading the older assembly.

So how would you troubleshoot this scenario.  I have taken number of .NET interviews and this most of the times goes unanswered so I thought I would write a small post about it.

So how would you to troubleshoot this..There are number of tools which you can use here but today I am going to discuss about a very basic one..Fusion Log

So, what is fusion,Fusion is a process to identify and load the assemblies requested by the .NET application. Now this process can be recorded

and luckily .NET framework comes with a tool that allows you to record the loading process. It records the following


  • Which assembly was requested
  • The location from where it was loaded (It records the complete probing process)
  • any errors
  • etc..

how it works:

Simply go to .NET command prompt and type fuslogvw.exe and enable the log.Basically you need to specify the location to keep the log etc..Once done, run any .net app and check the logs.
It will create the log for each .NET assembly it loads. It will tell you how it probe the assembly.

lets say you don’t have .net framework command prompt, still you can enable it by using the registry editor.

Create a log folder (default: C:\fusionlogs)
Add HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion\LogPath and set it to the log folder
Set HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion\LogFailures to 1
Optionally set HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion\ForceLog to 1
Optionally set HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion\LogResourceBinds to 1

For more information, visit: http://msdn.microsoft.com/en-us/library/e74a18c4%28v=vs.71%29.aspx

Try this tool and see how it can helps you specially debugging the problem of loading .NET assemblies.

next I am going to talk about the problems related to the file system and registry while working in .net application…any guesses????


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