using System.Configuration;
using System.Data.SqlClient;

class PerdiemSQL
{
    public void connectToDB(
        string commandString,
        string connectionStringKey = @"default")
    {
        string connectionString = ConfigurationManager.ConnectionStrings[connectionStringKey].ConnectionString;
        using(SqlConnection residentConnection = new SqlConnection(connectionString))
        {
            SqlCommand residentCommand = new SqlCommand(commandString, residentConnection);
            residentConnection.Open();

            using (SqlDataReader residentReader = residentCommand.ExecuteReader())
            {
                while (residentReader.Read())
                {
                //   pump pipe
                }
            }
        }
    }
}