How to load Automatically a database

Hi,

That if you select and connectionstring that the database will automatically be loaded with a specific table - in this case: TripElement. Because I have it now hard coded, like this:

private string _connectionString = @"server=DEV12;database=prod_CycleTours_net2_backup_201107110300;uid=sa;pwd=misoft;";

I have a listbox with a list of connectionstrings and if you select an connectionstring from the listbox then automatically the database with the specific column will be loaded

I triied like this:

[code]
 private void btn_SelectDatabase_Click(object sender, EventArgs e)
  {


  using (var _connectionString = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
  using (var command = connection.CreateCommand())
  {
  command.CommandText = "SELECT ColumnName FROM [check]";
  connection.Open();
  using (var reader = command.ExecuteReader())
  {
  while (reader.Read())
  txtConfigurationName.Text = reader["TripElement"].ToString();
  }
  }
  }

[/code]