The following example accomplishes this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace InsertToDatabase
{
	public class InsertToDatabase
	{
		string connectionString = @"Data Source = ServerName; user id=UserName; password=P@sswd!; Initial Catalog = DatabaseName;";
		string query = "INSERT INTO Users (Firstname, Lastname, Email) VALUES ('Jared','Barneck','Jared.Barneck@somedomain.tld')";
		SqlConnection connection = new SqlConnection(connectionString);
		SqlCommand command = new SqlCommand(query, connection);
		connection.Open();
		command.ExecuteNonQuery();
		connection.Close();
	}
}