BindingFlags does not exist in .NET Core netstandard 1.2 class library

Question

In a .NET Core class library project targeting both net452 and netstandard1.3 frameworks, I'm trying to move the latter backwards to netstandard1.2 in order to extend back-compatibility.

Project uses BindingFlags enum and builds fine on net452, as well netstandard1.3, but it fails on netstandard1.2 with a number of errors, all looking either like:

CS0103 The name 'BindingFlags' does not exist in the current context

or like:

CS7069 Reference to type 'BindingFlags' claims it is defined in 'System.Reflection', but it could not be found

Currently, frameworks attribute in project.json is:

"frameworks": {
  "netstandard1.2": {
    "imports": [
      "dnxcore50",
    ],
    "dependencies": {
      "NETStandard.Library": "1.6.0",
      "runtime.any.System.Collections": "4.0.11",
      "System.Collections": "4.0.11",
      "System.Collections.NonGeneric": "4.0.1",
      "System.Console": "4.0.0",
      "System.IO.FileSystem": "4.0.1",
      "System.Reflection.TypeExtensions": "4.1.0",
      "System.Runtime.Serialization.Xml": "4.1.1",
      "System.Text.Encodings.Web": "4.0.0"
    }
  },
  "net452": {
    "frameworkAssemblies": {
      "System.IO": "",
      "System.Runtime.Serialization.Xml": "",
      "System.Xml": "",
      "System.Web": ""
    }
  }
},

and it already lists dependency from System.Reflection.TypeExtensions.

Show potential fixes popup suggests to install "System.Reflection": "4.3.0-preview1-24530-04", only to find that type still shows with the red squiggly line. Another Show potential fixes popup this second time suggests to install "System.Reflection.TypeExtensions": "4.3.0-preview1-24530-04". Of course without affecting the error, that's still there.

Building net452 side goes fine, errors are only on netstandard1.2 build.

What's wrong with this BindingFlags type?

Answer 1

According to the netstandard 1.5 diff the BindingFlags enum was added to the standard in the 1.5 version.

Before it was available through the System.Reflection.TypeExtensions package which only supports 1.3 or later so targetting 1.2 doesn't work.