install .net core on ubuntu

sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/dotnet-release/ xenial main" > /etc/apt/sources.list.d/dotnetdev.list' 
sudo apt-key adv --keyserver apt-mo.trafficmanager.net --recv-keys 417A0893 
sudo apt-get update 
sudo apt-get install dotnet-dev-1.0.0-preview2-003131

cd ~/ 
mkdir SqlServerSample 
cd SqlServerSample 
dotnet new

add lines to .json file
"dependencies": { 
"System.Data.SqlClient": "4.3.0"

edit program.cs

using System;
using System.Text;
using System.Data.SqlClient;

namespace SqlServerSample
{
class Program
{
static void Main(string[] args)
{
try
{
// Build connection string
SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
builder.DataSource = "localhost"; // update me
builder.UserID = "sa"; // update me
builder.Password = "your_password"; // update me
builder.InitialCatalog = "master";

// Connect to SQL
Console.Write("Connecting to SQL Server ... ");
using (SqlConnection connection = new SqlConnection(builder.ConnectionString))
{
connection.Open();
Console.WriteLine("Done.");
}
}
catch (SqlException e)
{
Console.WriteLine(e.ToString());
}

Console.WriteLine("All done. Press any key to finish...");
Console.ReadKey(true);
}
}
}

dotnet restore

dotnet run