xml

<connectionStrings>

  <add name="MyConnectionString" connectionString="Data Source=.SQLEXPRESS01;Initial Catalog=Cells;Integrated Security=False;User ID=a2profile;Password=a2profile;" />

</connectionStrings>

csharp

using System.Configuration;

...



string connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;

csharp

SqlConnection sqlConnection = new SqlConnection(connectionString);

csharp

public class DataBase

{

    private SqlConnection connection;



    public SqlConnection GetConnection()

    {

        if (connection == null)

        {

            string connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;

            connection = new SqlConnection(connectionString);

        }

        

        return connection;

    }

    

    public void openConnection()

    {

        try

        {

            SqlConnection connection = GetConnection();

            connection.Open();

        }

        catch (Exception ex)

        {

            MessageBox.Show("Ошибка подключения к базе данных: " + ex.Message);

            Environment.Exit(0); // закрыть приложение

        }

    }

    

    public void closeConnection()

    {

        try

        {

            SqlConnection connection = GetConnection();

            connection.Close();

        }

        catch (Exception ex)

        {

            MessageBox.Show("Ошибка при закрытии подключения к базе данных: " + ex.Message);

        }

    }

}