String interpolation in a Razor view?

Question

Is this supported?

If so, is there some trick to enabling it? I'm assuming Razor isn't using a new enough compiler...? The VS2015 IDE seems to be fine with it but at runtime I am getting

CS1056: Unexpected character '$'

Answer 1

Update:

Starting in Visual Studio 2015 Update 1, there is a simple process in the GUI to do the steps below for you. Simply right-click your web project and select "Enable C# 6 / VB 14". More information is available on the MSDN blog post, "New feature to enable C# 6 / VB 14".

Since this answer was written, this functionality has been added with the assistance of a NuGet package.

Add this Nuget package to your solution if you are using MVC5.

https://www.nuget.org/packages/Microsoft.CodeDom.Providers.DotNetCompilerPlatform/

The nuget package should modify your web.config, but check that the following configuration is in your web.config file (and if it isn't add it in):

  <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>

In MVC6, this is built-in.

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Original answer:

<div>
    @($"Hello {this.Model.SomeProperty}")
</div>

This only works in C# 6 with MVC6. Even if you are running MVC5 with the C# 6 compiler, it won't work.

The trick is that the razor parser is not smart enough to recognize some syntaxes yet, so you must wrap the whole thing in parentheses (you must do this when using the null-conditional operator (?.) in your razor views as well).

That said, string interpolation in Razor is a bit buggy at the moment in MVC6, so I wouldn't be surprised if there were some issues with it. whether or not they will be addressed is another matter.

Answer 2

1. Run the following command in your Package Manager Console to add a required CodeDom provider to your project. It also modify your web.config file automaticlly to add CodeDom require settings to it.

   Install-Package Microsoft.CodeDom.Providers.DotNetCompilerPlatform

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2. Restart the Visual Studio

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Note: As @Jake mentioned in his comment under this answer, if you have DotNetCompilerPlatform package already, So try to update it.