dotnet core - Native Cross Platform

Following my initial foray into the world of dotnet core I was very excited at what this offers. I can now take my C# code and really easily build and run it on any of my Windows, Linux and Mac platforms. True, I've been able to do that for a while with Mono, but the tooling seems to be making it a common operation on each and something that I can see the toolchain working well with on Docker and Cloud deployments.

Pumped up by this and reading through the final post that I mentioned in the last article I wanted to have a look at a native build of the application. There are a number of reasons for this that we'll dig in to. First of all the build completed in the last post is a dotnet portable application. Take a look in bin/Debug/netcoreapp1.0 and you can see this is creating a dll that the dotnet core exe uses to run the application. It's a jumping off point. It also means that you need to have the dotnet core runtime and libraries already installed. This is possible with Linux deploys and there are a bunch of examples out there and with a bit more faff it's possible with Docker, but I was interested in making this really simple by being able to copy over a single file.

What's more, I had a taste for wanting to be able to build on my Windows or Mac box and create the Linux cross-compiled version that I could then put on a Docker container and use in the Cloud.

In the post there is a very nice walk through of setting up for various native compile targets. This requires some modifications to the basic project.json file as follows:

{
  "version": "1.0.0-*",
  "buildOptions": {
    "debugType": "portable",
    "emitEntryPoint": true
  },
  "dependencies": {
  },
  "frameworks": {
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "version": "1.0.0"
        }
      },
      "imports": "dnxcore50"
    }
  },
  "runtimes": {
    "win7-x64": {},
    "ubuntu.14.10-x64": {}
  }
}

A new runtimes section has been added with some targets. A list of the supported runtimes can be found in the RID catalog.

Restoring and building now gives us a new directory bin/Debug/netcoreapp1.0/win7-x64 with the following contents:

Which you can see clearly this time now contains the dotnetcore.exe that kicks things off. However, this does not look like a native exe to me and more disappointingly the ubuntu version seems to have been missed completely.

Forgetting the cross-compile for the moment, certainly there should be a native build and then I could go through some hassle, setup a Linux machine and build on that. I took a look for some other examples. This post gives some very positive early looks at dotnet core and native compiling. This time using the dotnet compile --native option. It seems that this is from a very early pre-release version and the compile option has now been scrubbed in favour of dotnet build --native.

Digging a bit more it seems that both cross-compiling and indeed native compiling has been disabled in RC2. It seems I'm not the only one to have struggled with this and taken a look also at using the --Native switch on the build option.

Not wanting to be deterred completely I decided to uninstall RC2 as I had Preview2 and install an earlier version. Getting hold of Preview1 was next to impossible. I found how to get dotnet core versions with PowerShell. After faffing around a bit I was blocked due to scripting being unhelpfull disabled on the machine I was using. Undeterred I did finally find a Preview1 msi, installed, tested and once again the native build option was not available.

As a last stab, I did download the dotnet cli source code and start kicking off a compile which didn't work directly in Visual Studio and I'd pretty much lost the energy at that point to have another round with PowerShell on another machine.

This is most frustrating as although I could probably fight this through to get it working on Docker, I'm also interested if some of the backend functions I have could be easily used as AWS Lambdas. This would allow me to reuse some existing C# code just when needed without the costs of porting. It might not be the fastest in run-time, but certainly would be beneficial in terms of reuse. This post got it to work, presumably with a build where the native option was still available.

Well, hopefully native and cross-compile will come back as I think for now I'll need to put this to one side until RC2 is out the door.