Defining Symbols for Pre-Processor Directives

[dazinator]

I'm using VS with preview 1 release of tooling, working on an RC2 based application.

I'm looking at code like this:

#if !DNXCORE50
        [XmlAttribute]
#endif

That directive seems to work - but where does it come from and is there a standard list somewhere for each of the frameworks?

What i'd like to know is:

1. What is the compilation directive for NETSTANDARD1.5 (I have tried NETSTANDARD1_5 and NETSTANDARD15
2. How do I configure my own.

I tried doing this in project.json but it didn't work:

"frameworks": {
  "netstandard1.5": {
      "define": [ "NETSTANDARD", "NETSTANDARD1_5", "MYOWN" ],
}

[dazinator]

I'm an idiot. I should have used intellisense within the project.json

"netstandard1.5": {
"buildOptions": { "define": [ "NETSTANDARD", "NETSTANDARD1_5", "MYOWN" ] },