Conditional compilation symbol for a .NET Core class library

Since xproj was discontinued, here is how it is done in the new Visual Studio 2017 .csproj files.

<PropertyGroup Condition="'$(TargetFramework)' == 'netstandard1.3' Or '$(TargetFramework)' == 'netstandard1.6' ">
    <DefineConstants>NET_CORE</DefineConstants>
</PropertyGroup>

Then instead of:

private TypeInfo GetTypeInfo(Type type)
{
    #if NETSTANDARD1_3 || NETSTANDARD1_6
        // Core
    #else
        // Full framework
    #endif
}

You can do:

private TypeInfo GetTypeInfo(Type type)
{
    #if NET_CORE
        // Core
    #else
        // Fullframework
    #endif
}

See here for more details on multi-targeting: Developing Libraries with Cross Platform Tools, How to Multitarget

Conditional variables should be defined in your project.json file for RC2, and I have a sample project here,

Port #SNMP from .NET Core RC1 to RC2

But there are also predefined ones from this article,

Developing Libraries with Cross Platform Tools