如何在事件处理程序中使用消息框

Question

Context : I have a TreeView in one of my form. Depending on the selection of that TreeView I load a UserControl in a pannel. One pannel is readonly but in the other pannel the user can modifie/add data that I save in a database. If the user try to make a new selection in the TreeView (event BeforeSelect) and he is in the second control (mod/add) and he have unsaved data, I want to ask him if he want to save before loading the new control. The problem is that when the messagebox is shown the event kinda lost the focus and is called in loop (around 20 times). In addition, no matter what the user click on the messagebox (yes save or no just load new control) as no influence.

So my question is : Is there anyway to ask the user what he want to do in the event handler?

I hope i was clear enought, sorry English isn't my first langage

/edit

Here the code from BeforeSelect and IsCtrlFormUnsave

private void tv_BeforeSelect(object sender, TreeViewCancelEventArgs e)
{
    if (IsCtrlFormUnsave())
    {
        e.Cancel = true;
        //Invoke(new Action(AvertirUser)); //this is in case the save action didn't worked
    }
}

private bool IsCtrlFormUnsave()
{
    if (_ctrlForm != null && _ctrlForm.unsavedChange)
    {
        DialogResult dr = MessageBox.Show("Le formulaire présentement ouvert contient des données qui n'ont pas été sauvegardées. Voulez-vous les enregistrés avant de poursuivre?",
                                                "Attention!", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
        if (dr == DialogResult.Yes)
            if (!_ctrlForm.Save())
                return true;

        _ctrlForm = null;
    }
    return false;
}

The function AvertirUser only containt a messagebox

Answer 1

you need to check if the selection is the user action or a revert action of user cancel etc.

one way of fixing it is to add another bool value:

bool IsChecked=false;
private void tv_BeforeSelect(object sender, TreeViewCancelEventArgs e)
{
    if (!IsChecked && IsCtrlFormUnsave()) //Check if it's already confirmed with the user
    {
        e.Cancel = true;           
    }
}

private bool IsCtrlFormUnsave()
{
    IsChecked=true; //set it to true to jump out of the loop
    if (_ctrlForm != null && _ctrlForm.unsavedChange)
    {   

        DialogResult dr = MessageBox.Show("Le formulaire présentement ouvert contient des données qui n'ont pas été sauvegardées. Voulez-vous les enregistrés avant de poursuivre?",
                                                "Attention!", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
        if (dr == DialogResult.Yes)
            if (!_ctrlForm.Save())
                return true;

        _ctrlForm = null;
    }
    return false;
}

And remember to reset IsChecked=false when you load second control again.

Answer 2

Add a Close() method to your UserControl , and place the messagebox code there. Then it can call its own Save() method:

    public void Close()
    {
        if (this.unsavedChange)
        {
            DialogResult dr = MessageBox.Show("Le formulaire présentement ouvert contient des données qui n'ont pas été sauvegardées. Voulez-vous les enregistrés avant de poursuivre?",
                                                    "Attention!", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
            if (dr == DialogResult.Yes)
            {
                this.Save();
            }
        }
    }

Back in the Form, you can do:

    private void tv_BeforeSelect(object sender, TreeViewCancelEventArgs e)
    {
        if (_ctrlForm != null)
        {
            _ctrlForm.Close();
            _ctrlForm.Dispose();
            _ctrlForm = null;
        }
    }