How to Install dotnet core on Ubuntu 16.04.5 ?

Before installing .NET, you'll need to register the Microsoft key, register the product repository, and install required dependencies. This only needs to be done once per machine.

Open a command prompt and run the following commands:

wget -qO- https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.asc.gpg
sudo mv microsoft.asc.gpg /etc/apt/trusted.gpg.d/
wget -q https://packages.microsoft.com/config/ubuntu/18.04/prod.list 
sudo mv prod.list /etc/apt/sources.list.d/microsoft-prod.list

wget -q https://packages.microsoft.com/config/ubuntu/16.04/packages-microsoft-prod.deb
sudo dpkg -i packages-microsoft-prod.deb

Install the .NET SDK

Update the products available for installation, then install the .NET SDK.

In your command prompt, run the following commands:

sudo apt-get install apt-transport-https
sudo apt-get update
sudo apt-get install dotnet-sdk-2.1