How to make razor view engine to use c# 6.0

I believe this is due to a bug in the templates for web.config when the project is upgraded to a newer version of the .net framework.

I was able to fix this by going in to web.config, finding the system.codedom node, and changing the content to look like this:

<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>

If you are running this from a 4.5.1 project, upgrading to 4.5.2 might fix it.

Otherwise, it is recommended to install this NuGet package to provide the new functionalities: Microsoft.CodeDom.Providers.DotNetCompilerPlatform

So doing something like this:

<p>@Model.Person?.Name</p>

Might work. If it doesn't, try being explicit like this:

<p>@(Model.Person?.Name)</p>

Other answers are quite good, but I found a good and short article that definitively clarify the steps for this issue: https://cpratt.co/using-csharp-6-or-7-with-mvc-5/

In short:

1. In the Package Manager Console install Install-Package Microsoft.CodeDom.Providers.DotNetCompilerPlatform

2. checka/alters you Web.config with the following lines at the end:

<system.codedom>
  <compilers>
    <compiler language="c#;cs;csharp"
      extension=".cs"
      type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.4.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
      warningLevel="4"
      compilerOptions="/langversion:7 /nowarn:1659;1699;1701" />
    <compiler language="vb;vbs;visualbasic;vbscript"
      extension=".vb"
      type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.4.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
      warningLevel="4"
      compilerOptions="/langversion:15 /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+" />
  </compilers>
</system.codedom>