I’ve just needed to upgrade a web part installed in our SharePoint farm. I could have gone to Central Administration, retracted, then removed the solution, but I wanted a quicker procedure.
I originally installed the web part using the Add-SPSolution PowerShell command. I first attempted to update the web part using Add-SPSoultion -LiteralPath %path to updated wsp file%, but received the error “A solution with the name …. already exists in the solution store.”
I realised I needed to use the Update-SPSolution PowerShell command. This required two extra parameters, the name of the web part solution to be updated and the -GACDeployment parameter. When I ran this command, the existing web part was automatically updated using a SharePoint timer job.