I had the same issue and adding the following package to my project.json dependencies fixed it for me:
"Microsoft.NETCore.Portable.Compatibility": "1.0.1-rc2-24027",
This package enables compatibility with mscorlib-based PCLs.
I had the same issue and adding the following package to my project.json dependencies fixed it for me:
"Microsoft.NETCore.Portable.Compatibility": "1.0.1-rc2-24027",
This package enables compatibility with mscorlib-based PCLs.