c# - Compiler directives for targeting several frameworks using .NET Core -

i have library targeting .net core , net45 @ point on code need use reflection this:

var type = obj.gettype(); var properties = type.getproperties().tolist();  if (type.isprimitive || type.isenum || properties.count == 0)     return new dictionary<string, object> { { unnamed, obj } }; 

now porting library support .net core made new .net core library project, project.json

{   "version": "1.0.0",   "dependencies": {     "wen.logging.abstractions": "1.0.0"   },   "frameworks": {     "net45": {       "frameworkassemblies": {         "system.reflection": "4.0.0.0"       },       "dependencies": {         "newtonsoft.json": "6.0.4",         "nlog": "4.3.5"       }     },     "netstandard1.6": {       "imports": "dnxcore50",       "dependencies": {         "netstandard.library": "1.6.0",         "system.reflection.typeextensions": "4.1.0",         "newtonsoft.json": "8.0.2",         "nlog": "4.4.0-*"       }     }   } } 

added classes , compiler complains type.isprimitive , types.isenum properties thought use compiler directives this:

var type = obj.gettype(); var properties = type.getproperties().tolist();  #if net45      if (type.isprimitive || type.isenum || properties.count == 0)     return new dictionary<string, object> { { unnamed, obj } };  #elif netstandard16  //... code  #endif 

once code inside net45 grayed out (i think because vs seeing .net core) no matter tag set between #elif , #endif grayed. have tried #else , can do:

var typeinfo = type.gettypeinfo(); if(typeinfo.isprimitive || typeinfo.isenum || properties.count == 0)     return new dictionary<string, object> { { unnamed, obj } }; 

however question remains:

what tags should use on code on compiler directives #if target several frameworks on same project/library?

while doing research on .net core came across this question , in accepted answer there in project.json file code caught eye, here snippet:

"frameworks": { "net46": {   "buildoptions": {     "define": [ "net46" ]   } }, 

as can see inside buildoptions there define: [ net46 ] tag can use along #if , #elif directives. if don't know (or there isn't) way refer versions of framework use own.