singleton

singleton.cs

public sealed class DBConnection
{
  private static SqlConnection instance = null; 
  private static readonly object padlock = new object();

  private DBConnection()
  {
  }


  public static SqlConnection Instance
  {
    get
    {
      lock (padlock)
      {
        if (instance == null)
        {
            instance = new SqlConnection(conStr);
        }
        return instance;
      }
    }
  }
  
  public static void Open() 
  {
    if (instance != null)
      instance.Open();
  }
  public static void Close()
  {
    if (instance != null)
      instance.Close();
  }
}