You need an underscore, _
, instead of a point:
NETCOREAPP1_0
or the more recent NETCOREAPP1_1
and NETCOREAPP2_0
The documentation for Target frameworks in SDK-style projects includes a list for the different preprocessor symbols.
.NET Framework
NETFRAMEWORK, NET48, NET472, NET471, NET47, NET462, NET461, NET46, NET452, NET451, NET45, NET40, NET35, NET20
.NET Standard
NETSTANDARD, NETSTANDARD2_1, NETSTANDARD2_0, NETSTANDARD1_6, NETSTANDARD1_5, NETSTANDARD1_4, NETSTANDARD1_3, NETSTANDARD1_2, NETSTANDARD1_1, NETSTANDARD1_0
.NET 5+ and .NET Core
NET, NET6_0, NET6_0_ANDROID, NET6_0_IOS, NET6_0_MACOS, NET6_0_MACCATALYST, NET6_0_TVOS, NET6_0_WINDOWS, NET5_0, NETCOREAPP, NETCOREAPP3_1, NETCOREAPP3_0, NETCOREAPP2_2, NETCOREAPP2_1, NETCOREAPP2_0, NETCOREAPP1_1, NETCOREAPP1_0
Mono
For Mono you can usually use the NetFramework monikers known by your version of Mono. For instance, Mono 6.12 includes all NetFramework versions from 2.0 to 4.8. But if you must recognise Mono per se, then MONO
and __MonoCS__
should both be defined.