How to unregister/undeploy Custom Workflow

Hi Guys/Experts,

Please guide me how to undeploy(unregister) a custom workflow in CRM 2015?

I have created a custom workflow which has also updated the RegisterFile.crmregister config file and deployed from Visual Studio.

It then reflected while building the new workflow. However, for some reasons I want to undeploy it, so I have deleted the file from the project, removed the entry from crmregister file, but I get below error. The error was also coming before trying to undeploy.

Error 79 Error registering plugins and/or workflows. Assembly bin\Debug\Solera.CRM.Workflow.dll could not be found. C:\Program Files (x86)\MSBuild\Microsoft\CRM\Microsoft.CrmDeveloperTools.12.targets 176 4 CrmPackage

Any inputs is much appreciated.

Thanks,

Shameem