CS1617: Option "6" is invalid for/langversion; must be ISO-1, ISO-2, 3, 4, 5, or Default

Today, a new MVC project was created with VS2015. The error CS1617: Option "6" is invalid for/langversion; must be ISO-1, ISO-2, 3, 4, 5, or Default

See the detailed error message below (note the red text: /langversion:6)

C:\Program Files (x86) \iis express> "C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe"/t:library/ UTF8OUTPUT/R: "C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3 \202c2dc7\15bae5b1_b7ced001\microsoft.owin.security.google.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ System.web.services\v4.0_4.0.0.0__b03f5f7f11d50a3a\system.web.services.dll "/r:" C:\Windows\Microsoft.Net\ Assembly\gac_msil\system.servicemodel.web\v4.0_4.0.0.0__31bf3856ad364e35\system.servicemodel.web.dll "/r:" \ c \ Windows\microsoft.net\assembly\gac_msil\system.xml.linq\v4.0_4.0.0.0__b77a5c561934e089\system.xml.linq.dll "/r: "C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\d986d339\ Dd58d2b1_b7ced001\microsoft.owin.security.facebook.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP . NET Files\root\e4d07940\88f2ce54\assembly\dl3\6edd4214\af23c6b1_b7ced001\microsoft.owin.host.systemweb.dll "/r: "C:\Windows\microsoft.net\assembly\gac_msil\system.web.dynamicdata\v4.0_4.0.0.0__31bf3856ad364e35\ System.Web.DynamicData.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\ 88f2ce54\assembly\dl3\310df7bb\03654bb0_b7ced001\webgrease.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp\ Temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\11a328a2\ea601eb0_b7ced001\ Microsoft.Web.Infrastructure.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_ 4.0.0.0__b03f5f7f11d50a3a\system.configuration.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ Microsoft.visualstudio.web.pageinspector.loader\v4.0_1.0.0.0__b03f5f7f11d50a3a\ Microsoft.VisualStudio.Web.PageInspector.Loader.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ System.web.applicationservices\v4.0_4.0.0.0__31bf3856ad364e35\system.web.applicationservices.dll "/r:" C:\Users\ Lizhaoyang\appdata\local\temp\temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\a03e25be\c4e10fb0_ B7ced001\system.web.webpages.deployment.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\ E4d07940\88f2ce54\assembly\dl3\c90a79f0\463eccb1_b7ced001\microsoft.owin.security.dll "/r:" C:\Users\lizhaoyang\ Appdata\local\temp\temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\6bf659b7\28cc10b0_b7ced001\ System.Web.WebPages.Razor.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\ 88f2ce54\assembly\dl3\32287575\cbcd22b0_b7ced001\system.web.mvc.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp \temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\77df798b\8ce4abb1_b7ced001\ Microsoft.AspNet.Identity.Core.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Drawing\v4.0_4.0.0.0_ _b03f5f7f11d50a3a\system.drawing.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_32\System.Web\v4.0_4.0.0.0__ B03f5f7f11d50a3a\system.web.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_32\System.EnterpriseServices\v4.0_ 4.0.0.0__b03f5f7f11d50a3a\system.EnterpriseServices.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\e4d07940\88f2ce54 \assembly\dl3\a528d8a7\a181b5b1_b7ced001\microsoft.aspnet.identity.entityframework.dll "/r:" C:\Windows\ Microsoft.net\assembly\gac_msil\system.workflowservices\v4.0_4.0.0.0__31bf3856ad364e35\ System.WorkflowServices.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Runtime.Serialization\v4.0_ 4.0.0.0__b77a5c561934e089\system.runtime.serialization.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp\ Temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\baf55bfc\982780b2_b7ced001\ Microsoft.CodeDom.Providers.DotNetCompilerPlatform.dll "/r:" C:\Windows\Microsoft.NET\Framework\v4.0.30319\ Mscorlib.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\e4d07940\88f2ce54\assembly\ Dl3\86633596\213d42b0_b7ced001\antlr3.runtime.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3\f73c1556\26bb32b1_b7ced001\entityframework.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\e4d07940\88f2ce54 \assembly\dl3\8fc9e967\95c1d8b1_b7ced001\microsoft.owin.security.cookies.dll "/r:" C:\Users\lizhaoyang\AppData\ Local\temp\temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\3bd9efc2\8e9fb0b1_b7ced001\ Microsoft.AspNet.Identity.Owin.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\ E4d07940\88f2ce54\assembly\dl3\3286340f\2cdcdeb1_b7ced001\microsoft.owin.security.oauth.dll "/r:" C:\Windows\ Microsoft.net\assembly\gac_32\system.data\v4.0_4.0.0.0__b77a5c561934e089\system.data.dll "/r:" C:\Windows\ Microsoft.net\assembly\gac_msil\system\v4.0_4.0.0.0__b77a5c561934e089\system.dll "/r:" C:\Windows\Microsoft.Net\ Assembly\gac_msil\system.activities\v4.0_4.0.0.0__31bf3856ad364e35\system.activities.dll "/r:" C:\Users\ Lizhaoyang\appdata\local\temp\temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\8c100c1b\583033b1_ B7ced001\entityframework.sqlserver.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.Extensions\v4.0_4.0.0.0__31bf3856ad364e35\ System.Web.Extensions.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\ 88f2ce54\assembly\dl3\daf7a022\5aa5c0b1_b7ced001\microsoft.owin.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp \temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3\51b1a9d2\067e10b0_b7ced001\system.web.webpages.dll " /r: "C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3\6007dc0c\ Bf33f9b0_b7ced001\newtonsoft.json.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\ E4d07940\88f2ce54\assembly\dl3\a23f30c4\e975f3b1_b7ced001\microsoft.owin.security.microsoftaccount.dll "/r:" \ c \ Windows\microsoft.net\assembly\gac_msil\system.servicemodel\v4.0_4.0.0.0__b77a5c561934e089\ System.ServiceModel.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.CSharp\v4.0_4.0.0.0__ B03f5f7f11d50a3a\microsoft.csharp.dlL "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\ 06c08773\2c080b94_bcced001\mvcmovie.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ System.servicemodel.activation\v4.0_4.0.0.0__31bf3856ad364e35\system.servicemodel.activation.dll "/r:" \ c \ Windows\microsoft.net\assembly\gac_msil\system.servicemodel.activities\v4.0_4.0.0.0__31bf3856ad364e35\ System.ServiceModel.Activities.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__ B77a5c561934e089\system.core.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. files\root\ E4d07940\88f2ce54\assembly\dl3\d320b303\96ac03b0_b7ced001\system.web.razor.dll "/r:" C:\Users\lizhaoyang\AppData \local\temp\temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3\c7d2e085\a23cbab1_b7ced001\owin.dll "/R:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ComponentModel.DataAnnotations\v4.0_4.0.0.0__ 31bf3856ad364e35\system.componentmodel.dataannotations.dll "/r:" C: \users\lizhaoyang\appdata\local\temp\temporary ASP. files\root\e4d07940\88f2ce54\assembly\dl3\dd752b88\ 6f630ab0_b7ced001\system.web.optimization.dll "/R:" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. \root\e4d07940\88f2ce54\assembly\dl3\4707f4f5\ff97ecb1_b7ced001\microsoft.owin.security.twitter.dll "/r:" \ c \ Windows\microsoft.net\assembly\gac_msil\system.identitymodel\v4.0_4.0.0.0__b77a5c561934e089\ System.IdentityModel.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Xml\v4.0_4.0.0.0__ B77a5c561934e089\system.xml.dll "/r:" C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Data.DataSetExtensions\ V4.0_4.0.0.0__b77a5c561934e089\system.data.datasetextensions.dll "/r:" C:\Users\lizhaoyang\AppData\Local\Temp\ Temporary ASP. Files\root\e4d07940\88f2ce54\assembly\dl3\fe48adbb\82450fb0_b7ced001\system.web.helpers.dll "/ Out: "C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\88f2ce54\app_ Global.asax.avkxmm6n.dll "/d:debug/debug+/optimize-/warnaserror/w:4/nowarn:1659;1699;1701;612;618 /langversion:6/nowarn:1659;1699;1701 "C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\88f2ce54\app _global.asax.avkxmm6n.0.cs "" C:\Users\lizhaoyang\AppData\Local\Temp\Temporary ASP. Files\root\e4d07940\ 88f2ce54\app_global.asax.avkxmm6n.1.cs

Then look at the error message:

Error CS1617: Option "6" is invalid for/langversion; must be ISO-1, ISO-2, 3, 4, 5, or Default

You can determine that the langversion parameter value specified at compile time is invalid and not supported. The supported parameters are listed, so we just need to change the value of the compile-time assignment, and then you can specify the compile-time parameters in config first.

Then press the value given to change to default to compile the run again. Get.

CS1617: Option "6" is invalid for/langversion; must be ISO-1, ISO-2, 3, 4, 5, or Default