New answers tagged assembly-references
It looks like when you deployed the tool it modified your CA web app in some way without being deployed there, by removing the web app without retracting the solution your central admin now expects that assembly to be present for some component. Deploying the solution to the central admin(or somewhere else) will solve the error. Once that is done you can ...
The DLL you are trying to add is most likely a 32-bit DLL. SharePoint development is done in 64-bit and thus it is not possible to use that DLL in your application. That also explains why SharePoint is not able to load your DLL since you only have the 32-bit DLL installed in your GAC after deployment.
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