Sql

 using (SqlConnection cn = new SqlConnection(connectionString))
{
commandString ="INSERT INTO table (Column1, Column2) " +
                                     "Values ('string', 1)");
    using (SqlCommand cm = new SqlCommand(commandString, cn))
    {
        cn.Open();
        cm.ExecuteNonQuery();
    }
}

  using (SqlConnection cn = new SqlConnection(connectionString))
{
     cn.Open();
     commandString ="select * from table";
    using (SqlCommand cm = new SqlCommand(commandString, cn))
    {
      using (SqlDataReader myReader = new SqlDataReader())
    {
        myReader = cm .ExecuteReader();
        while(myReader.Read())
        {
            Console.WriteLine(myReader["Column1"].ToString());
            Console.WriteLine(myReader["Column2"].ToString());
        }
     }
    }
}