Adding PCL reference causes "System.Object is not defined" error - asp.net

Question

I have a PCL with this project.json:
{
"supports": {
"net46.app": {},
"uwp.10.0.app": {},
"dnxcore50.app": {}
},
"dependencies": {
"Microsoft.NETCore": "5.0.0",
"Microsoft.NETCore.Portable.Compatibility": "1.0.0",
"System.ServiceModel.Primitives": "4.0.0"
},
"frameworks": {
"dotnet": {
"imports": "portable-net452+win81"
}
}
}
When I add a reference to my asp.net 5 web app, the resulting web app's project.json looks like this:
{
"version": "1.0.0-*",
"compilationOptions": {
"emitEntryPoint": true
},
"dependencies": {
"Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
"Microsoft.AspNet.Mvc": "6.0.0-rc1-final",
"Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final",
"Microsoft.AspNet.StaticFiles": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.FileProviderExtensions" : "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.Json": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging.Console": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging.Debug": "1.0.0-rc1-final"
},
"commands": {
"web": "Microsoft.AspNet.Server.Kestrel"
},
"frameworks": {
"dnx451": {
"dependencies": {
"MyPcl": "1.0.0-*"
}
},
"dnxcore50": {
"dependencies": {
"MyPcl": "1.0.0-*"
}
}
},
"exclude": [
"wwwroot",
"node_modules"
],
"publishExclude": [
"**.user",
"**.vspscc"
]
}
Which from what I can tell should be correct, but it results in a couple of errors in the web app:
Predefined type 'System.Object' is not defined or imported MyWebApp.DNX 4.5.1 C:\source\MyWebAppStartup.cs
Predefined type 'System.Void' is not defined or imported MyWebApp.DNX 4.5.1 C:\source\MyWebApp\Startup.cs
Ive found 100 ways to fix this, none have worked, and Im just not getting it. Any help would be appreciated. (Im using VS2015)
EDIT: Restarting VS resolved those errors. Now there is only this error
Object reference not set to an instance of an object. MyWebApp C:\source\MyWebApp\DNX 1