Building a C# Cmdlet
====================

This example project demonstrates how to build your own C# cmdlet for
PowerShell. When built in the following manner, the resulting DLL can be
imported everywhere: Windows PowerShell with Desktop .NET (FullCLR) and Open
PowerShell on Windows, Linux, and OS X with .NET Core (CoreCLR).

Setup
-----

We use the [.NET Command Line Interface][dotnet-cli] (`dotnet`) to build the
cmdlet library. Install the `dotnet` tool and ensure `dotnet --version` is at
least `1.0.0-rc2`.

.NET CLI uses a `project.json` file for build specifications:

```json
{
    "name": "SendGreeting",
    "description": "Example C# Cmdlet project",
    "version": "1.0.0-*",

    "dependencies": {
        "Microsoft.PowerShell.5.ReferenceAssemblies": "1.0.0-*"
    },

    "frameworks": {
        "netstandard1.3": {
            "imports": [ "net40" ],
            "dependencies": {
                "Microsoft.NETCore": "5.0.1-*",
                "Microsoft.NETCore.Portable.Compatibility": "1.0.1-*"
            }
        }
    }
}
```

Note that no source files are specified. .NET CLI automatically will build all
`.cs` files in the project directory.

Going through this step-by-step:

- `"name": "SendGreeting"`: Name of the assembly to output (otherwise it
  defaults to the name of the containing folder).

- `"version": "1.0.0-*"`: The wild-card can be replaced using the
  `--version-suffix` flag to `dotnet build`.

- [Microsoft.PowerShell.5.ReferenceAssemblies][powershell]: Contains the SDK
  reference assemblies for PowerShell version 5. Targets the `net40` framework.

- [netstandard1.3][]: The target framework for .NET Core portable libraries.
  This is an abstract framework that will work anywhere its dependencies work.
  Specifically, the 1.3 version allows this assembly to work even on Windows
  PowerShell with Desktop .NET.

- `"imports": [ "net4" ]`: Since the PowerShell reference assemblies target the
  older `net40` framework, we `import` it here to tell `dotnet restore` that we
  know we're loading a possibly-incompatible package.

- [Microsoft.NETCore][netcore]: Provides a set of packages that can be used when
  building portable libraries on .NETCore based platforms.

- [Microsoft.NETCore.Portable.Compatibility][portable]: Enables compatibility
  with portable libraries targeting previous .NET releases like .NET Framework
  4.0. Required to build against the PowerShell reference assemblies package.

Other dependencies can be added as needed; refer to the
[.NET Core package gallery][myget] for package availability, name, and version
information.

Because the .NET Core packages are not yet released to NuGet.org, you also need
this `NuGet.config` file to setup the [.NET Core MyGet feed][myget]:

```xml
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="CI Builds (dotnet-core)" value="https://www.myget.org/F/dotnet-core/api/v3/index.json" />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
</configuration>
```

[dotnet-cli]: https://github.com/dotnet/cli#new-to-net-cli
[powershell]: https://www.nuget.org/packages/Microsoft.PowerShell.5.ReferenceAssemblies
[netstandard1.3]: https://github.com/dotnet/corefx/blob/master/Documentation/architecture/net-standard-applications.md
[netcore]: https://dotnet.myget.org/feed/dotnet-core/package/nuget/Microsoft.NETCore
[portable]: https://dotnet.myget.org/feed/dotnet-core/package/nuget/Microsoft.NETCore.Portable.Compatibility
[myget]: https://dotnet.myget.org/gallery/dotnet-core

Building
--------

.NET Core is a package-based platform, so the correct dependencies first need to
be resolved:

```
dotnet restore
```

This reads the `project.json` and `NuGet.config` files and uses NuGet to restore
the necessary packages. The generated `project.lock.json` lockfile contains the
resolved dependency graph.

Once packages are restored, building is simple:

```
dotnet build
```

This will produce the assembly `./bin/Debug/netstandard1.3/SendGreeting.dll`.

This build/restore process should work anywhere .NET Core works, including
Windows, Linux, and OS X.

Deployment
----------

In PowerShell, check `$env:PSMODULEPATH` and install the new cmdlet in its own
module folder, such as, on Linux,
`~/.powershell/Modules/SendGreeting/SendGreeting.dll`.

Then import and use the module:

```powershell
> Import-Module SendGreeting # Module names are case-sensitive on Linux
> Send-Greeting -Name World
Hello World!
```

You can also import by the path:

```powershell
> Import-Module ./bin/Debug/netstandard1.3/SendGreeting.dll
```