error CS1617: Invalid option '8.0'

Question

I am getting error while compiling the application.

CSC : error CS1617: Invalid option '8.0' for /langversion; must be ISO-1, ISO-2, 3, 4, 5 or Default [C:\gi

tlab\cms\CMS\Server\OpenText.WS.MS.Application\OpenText.WS.MS.Application\OpenText.WS.MS.Application.cspro

j]

Detailed Error:

"C:\gitlab\cms\CMS\build.xml" (install target) (1) ->

"C:\gitlab\cms\CMS\Server\OpenText.WS.MS.Application\OpenText.WS.MS.Application.sln" (Build target) (22) -

"C:\gitlab\cms\CMS\Server\OpenText.WS.MS.Application\OpenText.WS.MS.Application\OpenText.WS.MS.Application

.csproj" (default target) (23) ->

(CoreCompile target) ->

CSC : error CS1617: Invalid option '8.0' for /langversion; must be ISO-1, ISO-2, 3, 4, 5 or Default [C:\

gitlab\cms\CMS\Server\OpenText.WS.MS.Application\OpenText.WS.MS.Application\OpenText.WS.MS.Application.csp

roj]