I updated a custom workflow (pure c# code) in SharePoint. Everything looked fine at first, but now I found the following errors in the ULS-Log:

Load Workflow Assembly: System.IO.FileNotFoundException: Could not load file or assembly 'myWorkflow, Version=, Culture=neutral, PublicKeyToken=b9b1d87f2ba348a3' or one of its dependencies. The system cannot find the file specified. File name: 'myWorkflow, Version=, Culture=neutral, PublicKeyToken=b9b1d87f2ba348a3'
at [...]

I understand what this means but not how to solve it.

First of all: Changing the AssemblyVersion back to the old version and reinstalling the workflow is not an option as there are already new Workflows created.

So I think I got two Possibilities:

  1. Use Assembly Binding Rediretion. Can this be easily done? Can I maybe even create a feature for that without reinstalling the Workflow?
  2. "Tell" the old workflows to use the new version. Can this be done with PowerShell?

1 Answer 1


This is your generated assembly, all you need to do is update the workflow and then use Update-SPSoution. SharePoint will know to use old assemblies for workflows that are still running on the old workflow after you update. Whenever you update a workflow as a solution, it will use the new version first, but keep the old version if there are any running.

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