Question: I am using Apricity OS (based on Arch Linux). I want to install Dot Net Core. What is the command for installing it by pacman.

Answer: 
Edit: Please see [sunspots answer](https://unix.stackexchange.com/a/426669/220340) if you want to use Dot Net now because it is in the repositories now. This answer was written when it was not yet.

There are several packages pertaining to DotNetCore in the Archlinux User Repository (AUR). As noted in the answer by mpromonet, one of those is dotnet-cli. However, there is no need to install yaourt (or any other AUR helper) to install packages from AUR.

I know this will probably be too late for the OP, but for the sake of completeness, theses are the steps to install a package that is only in the AUR in Archlinux (or its derivates) without additional tools:

```
1) Make sure you have the base-devel group installed
2) Go to the website https://aur.archlinux.org/packages/ and search the package
3) On the page for that package, klick "Download snapshot" and save the package to your computer
4) Extract the package on your computer: tar xvf <package_name>.tar.gz
5) cd <package_name>
6) makepkg
7) If the build fails, saying that a dependency is not satisfied, download and install that dependency first: try pacman -S <dependency> or else follow these steps
8) When the build succeeded, install the package:
   sudo pacman -U <pkgname>-<version_number>.tar.xz

```

See also the AUR [entry](https://wiki.archlinux.org/index.php/Arch_User_Repository) in the Archlinux wiki for a more in-depth description of the AUR.
The packages for .NET Core are now available from the official Community repository.

If you only want to run .NET Core applications, you will need the [`dotnet-runtime`](https://www.archlinux.org/packages/?name=dotnet-runtime) package.

```
pacman -S dotnet-runtime

```

In case you also want to build .NET Core applications yourself, you need the [`dotnet-sdk`](https://www.archlinux.org/packages/?name=dotnet-sdk) package.

```
pacman -S dotnet-sdk

```