Using Tuple in VS2017, build failed but show no Error

Question

var range = (first: 1, end: 10);

When I build the project, there is no error in Error List window. but the output window writes:

1>....cs(41,38,41,39): error CS1026: ) expected

1>....cs(41,40,41,41): error CS1001: Identifier expected

1>....cs(41,40,41,41): error CS1002: ; expected

1>....cs(41,41,41,42): error CS1002: ; expected

1>....cs(41,41,41,42): error CS1513: } expected

========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

Only when I remove the code var range = (first: 1, end: 10); can this project build success.

By the way, I'm using .NET Framework 4.6.2 (not .Net Core) and I've installed the package System.ValueTuple

Answer 1

I solved this issue by updating the package Microsoft.Net.Compilers (to version 2.x.x) and changing /langversion in the config file (web.config/app.config) to 7:

  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:7 /nowarn:1659;1699;1701" />
    </compilers>
  </system.codedom>