public partial class MyDialog : Form
  {
    //------------------------------
    // Static Member Variables
    //------------------------------

    public static int InstanceCount = 0;

    //------------------------------
    // Constructors
    //------------------------------

    public MyDialog()
    {
      InitializeComponent();
      InstanceCount++;
    }

    //------------------------------
    // Overrides
    //------------------------------

    protected override void Dispose(bool disposing)
    {
      if (disposing && (components != null))
      {
        components.Dispose();
      }

      InstanceCount = Math.Max(InstanceCount - 1, 0);
      System.Diagnostics.Debug.WriteLine(string.Format("Disposing of a MyDialog object.  Instance count = {0}", InstanceCount));

      base.Dispose(disposing);
    }
  }

  //========================================

  public partial class MainForm : Form
  {
    //------------------------------
    // Member Variables
    //------------------------------

    protected MyDialog m_myDialog = null;

    //------------------------------
    // Constructors
    //------------------------------

    public MainForm()
    {
      InitializeComponent();
    }

    //------------------------------
    // Overrides
    //------------------------------

    protected override void OnDoubleClick(EventArgs e)
    {
      base.OnDoubleClick(e);

      System.Diagnostics.Debug.WriteLine("MainForm double-clicked...");

      if (MyDialog.InstanceCount == 0)
      {
        System.Diagnostics.Debug.Write("Instantiating a new instance of MyDialog...");

        try
        {
          m_myDialog = new MyDialog();
          m_myDialog.Show();

          System.Diagnostics.Debug.WriteLine(string.Format("instance #{0} created.", MyDialog.InstanceCount));
        }
        catch
        {
          if (m_myDialog != null)
            m_myDialog.Dispose();

          System.Diagnostics.Debug.WriteLine("failed.");
        }
      }

      else
        System.Diagnostics.Debug.WriteLine("Choosing NOT to instantiate a new instance of MyDialog.");
    }

    //------------------------------

    protected override void OnClosing(CancelEventArgs e)
    {
      base.OnClosing(e);

      if ((!e.Cancel) && (m_myDialog != null))
      {
        m_myDialog.Dispose();
        m_myDialog = null;
      }
    }
  }