Target specific framework in Class Library (Package) - asp.net

Question

I am attempting to use the new Class Library (Package) project in VS 2015.
I would like to target dnx451, so my package.json looks like this:
{
"version": "1.0.0-beta-1",
"description": "Foo",
"authors": [ "Foo" ],
"tags": [ "" ],
"projectUrl": "",
"licenseUrl": "",
"dependencies": {
"Newtonsoft.Json": "8.0.1",
"Microsoft.AspNet.Razor": "4.0.0-rc1-final",
"Microsoft.Extensions.Configuration": "1.0.0-rc1-final",
"Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-rc1-final",
"Microsoft.Extensions.Configuration.FileProviderExtensions": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.Json": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0-rc1-final",
"System.Net.Http": "4.0.1-beta-23516"
},
"frameworks": {
"dnx451": { }
}
}
Build is fine, and I get:
Recaptcha-dnxcore -> C:\Users\Epic\Documents\artifacts\bin\Foo\Release\Foo.1.0.0-beta-1.nupkg
Now I create a web project and edit its project.json file so that it targets only the dnx451 framework:
"frameworks": {
"dnx451": { }
},
When I add a reference to my Foo package, I get an error:
The dependency Foo 1.0.0-beta-1 in project WebApplication7 does not support framework DNX,Version=v4.5.1.
How can I create a Nuget package from a Class Library (Package) project that supports dnx451?
Per the comment below, here is the full project.json of the web app:
{
"userSecretsId": "aspnet5-WebApplication7-0b4c05f0-6435-486b-9738-1b6aa3daee2c",
"version": "1.0.0-*",
"compilationOptions": {
"emitEntryPoint": true
},
"dependencies": {
"EntityFramework.Commands": "7.0.0-rc1-final",
"EntityFramework.MicrosoftSqlServer": "7.0.0-rc1-final",
"Microsoft.AspNet.Authentication.Cookies": "1.0.0-rc1-final",
"Microsoft.AspNet.Diagnostics.Entity": "7.0.0-rc1-final",
"Microsoft.AspNet.Identity.EntityFramework": "3.0.0-rc1-final",
"Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
"Microsoft.AspNet.Mvc": "6.0.0-rc1-final",
"Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-rc1-final",
"Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final",
"Microsoft.AspNet.StaticFiles": "1.0.0-rc1-final",
"Microsoft.AspNet.Tooling.Razor": "1.0.0-rc1-final",
"Microsoft.Extensions.CodeGenerators.Mvc": "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.Configuration.UserSecrets": "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",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0-rc1-final",
"System.Net.Http": "4.0.1-beta-23516",
"Foo": "1.0.0-beta-1"
},
"commands": {
"web": "Microsoft.AspNet.Server.Kestrel",
"ef": "EntityFramework.Commands"
},
"frameworks": {
"dnx451": { }
},
"exclude": [
"wwwroot",
"node_modules"
],
"publishExclude": [
"**.user",
"**.vspscc"
],
"scripts": {
"prepublish": [ "npm install", "bower install", "gulp clean", "gulp min" ]
}
}

Answer 1

I followed the same procedure as mentioned in your question
I created both class library and web project in same solution, everything worked fine.
Since your are more focused on making it NuGet package target to dnx451. I created another web application in separate solution, yes it throws errors because NuGet packages named are many "Foo". I guess due to this restoring of packages is given issue as its referring to Global NuGet feed.
Then I tried referring "Foo" Nuget package locally using this link How to install a Nuget Package .nupkg file locally?
Ensure that newly create local Package Source should be on TOP and Offical NuGet second place.
After this, I restored web application in separate solution, it build fine and run properly also. Even I installed this NUGET in Console apps also
Hope this works out.

Answer 2

The class library should also have it's own project.json and define the frameworks that it supports:
"frameworks": {
"dnx451": { }
}

Answer 3

Don't add the version Number if you add a reference to a project, because it will search for the package on any Nugget feed.
Just add a reference to Foo, like this:
"Microsoft.Extensions.Logging.Debug": "1.0.0-rc1-final",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0-rc1-final",
"System.Net.Http": "4.0.1-beta-23516",
"Foo": ""
},

Answer 4

Have a look at this answer.
You can only add a direct reference to your class library project only if both projects are in the same solution.
If your projects are not in the same solution you have to go to your class library project properties, open Build tab and check Produce outputs on build option
NuGet package will be created in {SolutionDir}\artifacts\bin{ProjectName}{Configuration} directory on each project build.
To use the library, publish NuGet package to nuget.org or any other NuGet feed and add it to your project using Visual Studio (References ~> Manage NuGet Packages...) or to dependencies property in project.json.