Creating Delegate Events

问题:

I'm trying to create a delegate event that is accessible in another form. But the main form doesn't seen to be able to see my delegate. It say delegate name is not valid at this point. modal form

public partial class GameOverDialog : Window
{
   public delegate void ExitChosenEvent();
   public delegate void RestartChosenEvent();

   public GameOverDialog()
   {
      InitializeComponent();
   }

   private void closeAppButton_Click(object sender, RoutedEventArgs e)
   {
      ExitChosenEvent exitChosen = Close;
      exitChosen();
      Close();
   }

   private void newGameButton_Click(object sender, RoutedEventArgs e)
   {
      RestartChosenEvent restart = Close;
      restart();
      Close();
   }
}

Main form:

private void ShowGameOver(string text)
{
   var dialog = new GameOverDialog { tb1 = { Text = text } };
   dialog.RestartChosenEvent += StartNewGame();
   dialog.Show();
}

private void StartNewGame()
{
   InitializeComponent();
   InitializeGame();
}

After @Fuex's Help*

private void ShowGameOver(string text)
{
   var dialog = new GameOverDialog { tb1 = { Text = text } };
   dialog.RestartEvent += StartNewGame;
   dialog.ExitEvent += Close;
   dialog.Show();
}

回答1:

It doesn't work because delegate void RestartChosenEvent() declares the type of the reference which allows to encapsulate the method. So by using on it += StartNewGame gives an error. The right code is:

public partial class GameOverDialog : Window
{
    delegate void myDelegate();

    public myDelegate RestartChosenEvent;
    public myDelegate ExitChosenEvent;

    public GameOverDialog()
    {
        InitializeComponent();
    }

    private void closeAppButton_Click(object sender, RoutedEventArgs e)
    {
        ExitChosenEvent();
        this.Close();
    }

    private void newGameButton_Click(object sender, RoutedEventArgs e)
    {
        RestartChosenEvent();
        this.Close();
    }
}

Then in your main form you have to use StartNewGame, which is the pointer of the method to pass, rather than StartNewGame():

private void ShowGameOver(string text)
{
   var dialog = new GameOverDialog { tb1 = { Text = text } };
   dialog.RestartChosenEvent += StartNewGame;
   dialog.Show();
}

回答2:

The 'delegate name is not valid at this point' error can also occur when you're defining a delegate and not using the new keyword. For instance:

// In asp.net the below would typically appear in a parent page (aspx.cs page) that 
// consumes a delegate event from a usercontrol:
    protected override void OnInit(EventArgs e) 
    { 
        Client1.EditClientEvent += Forms_Client.EditClientDelegate(Client1_EditClientEvent); 
        //NOTE: the above line causes 'delegate name is not valid at this point' error because of the lack of the 'new' keyword.
        Client1.EditClientEvent += new Forms_Client.EditClientDelegate(Client1_EditClientEvent); 
        //NOTE: the above line is the correct syntax (no delegate errors appear)
    } 

To put this into context you can see the definition of the delegate below. In asp.net if you're defining usercontrol that needs to get a value from its parent page (the page hosting the control) then you'd define your delegate in the usercontrol as follows:

//this is the usercontrol (ascx.cs page):
    public delegate void EditClientDelegate(string num); 
    public event EditClientDelegate EditClientEvent; 
    //call the delegate somewhere in your usercontrol:
    protected void Page_Load(object sender, System.EventArgs e)
    {
        if (EditClientEvent != null) { 
            EditClientEvent("I am raised"); 
        }
    }