VS2015 新Web项目(C#6)出现CS1617错误的解决

VS2015新增了对C#6的支持.

在新的Web项目模板中通过引入nuget包Microsoft.CodeDom.Providers.DotNetCompilerPlatform:1.0.0并在web.config中添加

  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" />
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=&quot;Web&quot; /optionInfer+" />
    </compilers>
  </system.codedom>

来提供Razor的C#6.0支持(旧项目也可以通过自己添加来获得支持)

但是在当你修改了目标框架(例如从4.5升级到4.6)之后, 网站将会无法开启并提示

“/”应用程序中的服务器错误。

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编译错误

说明: 在编译向该请求提供服务所需资源的过程中出现错误。请检查下列特定错误详细信息并适当地修改源代码。 

编译器错误消息: CS1617: 选项“6”对 /langversion 无效；必须是 ISO-1、ISO-2、3、4、5 或 Default

源错误:

[没有相关的源行]

源文件:    行: 0 

显示详细的编译器输出:

C:Program Files (x86)IIS Express> "C:WindowsMicrosoft.NETFrameworkv4.0.30319csc.exe" /t:library /utf8output /R:"C:WindowsMicrosoft.NETFrameworkv4.0.30319Temporary ASP.NET Filesvs...


Microsoft (R) Visual C# Compiler version 4.6.0081.0

for C# 5
Copyright (C) Microsoft Corporation. All rights reserved.



This compiler is provided as part of the Microsoft (R) .NET Framework, but only supports language versions up to C# 5, which is no longer the latest version. For compilers that support newer versions of the C# programming language, see http://go.microsoft.com/fwlink/?LinkID=533240

error CS1617: 选项“6”对 /langversion 无效；必须是 ISO-1、ISO-2、3、4、5 或 Default

查看web.config中的配置, 发现已被自动修改为(似乎一般是改cs不改vb, 往低了改会连vb一起改)

  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CSharp.CSharpCodeProvider, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701">
        <providerOption name="CompilerVersion" value="v4.0"/>
      </compiler>
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.VisualBasic.VBCodeProvider, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=&quot;Web&quot; /optionInfer+">
          <providerOption name="CompilerVersion" value="v4.0"/>
      </compiler>
    </compilers>
  </system.codedom>

而这是无法正常工作的, 需要手动修改为最初的结果

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已反馈至https://connect.microsoft.com/VisualStudio/feedback/details/1607466

2015/07/31: 微软已确认