Sharing code between aspnet5 and "old" .net

If you want to share some common code between aspnet5 and regular csproj projects, you basically have three options:

create a nuget from the common library and push it to a shared nuget repository
use dnu wrap to wrap existing csproj into aspnet5 project.json
maintain two versions of your shared project - a project.json for aspnet5 and a csproj for regular .net

The last option is the most error-prone and harder to maintain, so I will just ignore it.

Shared nuget package

Sharing a library through nuget has many benefits:

versioning
easy restoration (devs don’t need to compile anything, just restore nuget packaget)
less projects to compile - shorter compilation time

If the shared code doesn’t change to often, I would go with a shared nuget repository. But if the shared code is constantly changed, going through pack-push-restore process could be painful and time-consuming.

Wrapping csproj with `dnu wrap`

There is one other way - dnu has a handy command named wrap. It wraps your existing .csproj files into project.json files that can be then referenced by aspnet5 projects.

You can do something like this:

Add a global.json file in the some top-level directory that contains your projects. In the projects section, list directories that contain your source-code, for example:
```
 {
     "projects": [ "src", "test" ],
     "sdk": {
         "version": "1.0.0-rc1-final"
     }
 }
```
In the same directory that contains global.json execute dnu wrap for each existing .csproj project.

dnu wrap src/my.project/my.project.csproj

This should create a directory wrap containing project.json files that wrap .csprojs. A sample file looks like this:

<!-- language: lang-json -->

	{
		"version": "1.0.0-*",
		"frameworks": {
			"net45": {
				"wrappedProject": "../../src/my.project/my.project.csproj",
				"bin": {
					"assembly": "../../src/my.project/obj/{configuration}/my.project.dll",
					"pdb": "../../src/my.project/obj/{configuration}/my.project.pdb"
				}
			}
		}
	}

Note that wrap directory is also added to projects section in global.json.

In your solution, add a new aspnet project and add a reference to the wrapped project. Just add:
```
 "my.project": ""
```

to dependencies section. Aspnet should automatically pick up global.json file in root directory, and will look for projects in all directories listed there, including wrap directory.

Now you’re good to go - you can use all classes from my.project, step into them while debugging, go to definition, etc. Note that in your solution, you still have the old csproj.

You can find a sample code here: https://github.com/heavymetaldev/aspnet5-wrap.

I suppose this may get a little complicated if you have some custom things in your projects, like conditional compilation, custom includes, etc.

Shared nuget package

Wrapping csproj with dnu wrap

Wrapping csproj with `dnu wrap`