Не инициализируется свойство Connection String

Всем привет !

Подскажите, почему не переменная setting остаётся со значением null ?

 public partial class Form1 : Form
{
    OleDbConnection connection = new OleDbConnection();
    public Form1()
    {
        InitializeComponent();
        this.connection.StateChange += new System.Data.StateChangeEventHandler(this.connection_StateChange);

    }
    static string GetConnectionStringByName(string name)
    {
        string returnValue = null;
        ConnectionStringSettings settings =
            ConfigurationManager.ConnectionStrings[name];
        if (settings != null)
            returnValue = settings.ConnectionString;
        return returnValue;
    }

    string testConnect = GetConnectionStringByName("DBConnect.NorthwindConnectionString");
private void toolStripButton1_Click(object sender, EventArgs e)
    {
        try
        {
            if (connection.State != ConnectionState.Open)
            {
                connection.ConnectionString = testConnect;
                connection.Open();
                MessageBox.Show("Соединение с базой данных выполнено успешно");
            }
            else
            {
                MessageBox.Show("Соединение с базой данных уже установлено");
            }
        }
        catch (OleDbException XcpSQL)
        {
            foreach (OleDbError se in XcpSQL.Errors)
            {
                MessageBox.Show(se.Message, "SQL Error code" + se.NativeError,
                    MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }
        catch (Exception Xcp)
        {
            MessageBox.Show(Xcp.Message, "Unexpected Exception", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

В XML-ке добавил:

<?xml version="1.0" encoding="utf-8" ?> 
<configuration> 
  <connectionStrings> 
    <add name="DBConnect.NorthwindConnectionString" 
        connectionString="Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Northwind;Data Source=PC-9991-002518" 
        providerName="System.Data.OleDb" /> 
  </connectionStrings> 
 
</configuration>