Way to get VS2015 to validate for earlier syntax of C# to maintain compat with VS2013

Question

A specific problem I'm running into is that VS2015 allows you to use newer C# syntax, e.g. public string MyProperty => _myProperty; when targeting a .NET 4.0 framework project and then others opening the project in VS2013 get compiler errors.

Is there a way to configure VS2015 so that it warns or errors on features specific to C# 6? Or said another way, can I tell VS2015 which version of C# I'd like to compile against?

Answer 1

Yes, but this needs to be done on a per-project basis. It's an option available in the Build menu of the project properties. Click "Advanced" in the bottom right, then select the language version you want.

Note: There is a VS2015 bug (which has been fixed in Update 1) that causes false negatives on get-only auto-properties. To get the best results, make sure you have installed the latest update.

Answer 2

To piggyback on the accepted answer, to quickly implement this in 100's of projects, and to get all configurations and not just a specific configuration, I mass edited the csproj files and inserted a <LangVersion>5</LangVersion> node as the first child inside the first naked, unconditional <PropertyGroup> node:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
  <PropertyGroup>
    <LangVersion>5</LangVersion>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>