Visual Studio 2010 SharePoint project error - The language-neutral solution package was not found

We sometimes get this error when deploying SharePoint 2010 solutions from Visual Studio 2010:

Error occurred in deployment step ‘Retract Solution’: The language-neutral solution package was not found.

You can run get-spsolution powershell command without parameters to see which solutions are currently installed in the farm.Therefore you can use this powershell command to delete this solution manually:

(get-spsolution mysolution.wsp).Delete()

After you run this command, you can test your SharePoint 2010 solution in Visual Studio 2010 environment.