如何在MVP中将EventArgs从View传递到Presenter？

Question

I have an application based on MVP, WinForms and EntityFramework. At one form I need to validate cell value, but I don't know proper way to pass EventArgs from Validating event of DataGridView to my presenter.

I have this Form (unrelated code omitted):

public partial class ChargeLinePropertiesForm : Form, IChargeLinePropertiesView
{
    public event Action CellValidating;

    public ChargeLinePropertiesForm()
    {
        InitializeComponent();
        dgBudget.CellValidating += (send, args) => Invoke(CellValidating);
    }

    private void Invoke(Action action)
    {
        if (action != null) action();
    }

    public DataGridView BudgetDataGrid
    {
        get { return dgBudget; }
    }
}

Interface:

public interface IChargeLinePropertiesView:IView
{
    event Action CellValidating;
    DataGridView BudgetDataGrid { get; }
}

And this presenter:

public class ChargeLinePropertiesPresenter : BasePresenter<IChargeLinePropertiesView, ArgumentClass>
{
    public ChargeLinePropertiesPresenter(IApplicationController controller, IChargeLinePropertiesView view)
        : base(controller, view)
    {
        View.CellValidating += View_CellValidating;
    }

    void View_CellValidating()
    {
        //I need to validate cell here based on dgBudget.CellValidating EventArgs
        //but how to pass it here from View?

        //typeof(e) == DataGridViewCellValidatingEventArgs
        //pseudoCode mode on
        if (e.FormattedValue.ToString() == "Bad")
        {
            View.BudgetDataGrid.Rows[e.RowIndex].ErrorText =
                "Bad Value";
            e.Cancel = true;
        }
        //pseudoCode mode off
    }
}

Yes, I could expose a property through interface and set my EventArgs to this property in View to get them from Presenter, but this is ugly, isn't it?

Answer 1

public interface IChargeLinePropertiesView:IView
{
    event Action CellValidating;
    // etc..
}

Using Action is the problem here, it is the wrong delegate type. It doesn't permit passing any arguments. More than one way to solve this problem, you could use Action<CancelEventArgs> for example. But the logical choice is to use the same delegate type that the Validating event uses:

event CancelEventHandler CellValidating;

Now it is easy. In your form:

public event CancelEventHandler CellValidating;

public ChargeLinePropertiesForm() {
    InitializeComponent();
    dgBudget.CellValidating += (sender, cea) => {
        var handler = CellValidating;
        if (handler != null) handler(sender, cea);
    };
}

In your presenter:

void View_CellValidating(object sender, CancelEventArgs e)
{
   //...
   if (nothappy) e.Cancel = true;
}