C#: How to cancel the close action for a button that's set as the Accept or Cancel button on a form?

Question

I have a button btnOK on my form, with a DialogResult property of OK. The form's AcceptButton property is set to btnOK. So if I click the button, the form closes automatically.

Now, inside the btnOK_Click() method, I want to ability to cancel out of the close action, e.g. if there was an error I want to show a message box and not close the form.

How do I do it?

Answer 1

On error add:

this.DialogResult = DialogResult.None

Answer 2

IMO you just don't have to set DialogResult property on the button, but set it directly on your form in the btnOK_Click event:

private void btnOK_Click(object sender, EventArgs e)
{
    if (yeahLetsClose)
        this.DialogResult = DialogResult.OK;  // form will close with OK result
    // else --> form won't close...
}

BTW, AcceptButton property is related to ENTER key (when you press it on your form, the AcceptButton will be pressed)

Answer 3

Add an event handler for the form close event. The EventArgs parameter should have a Cancel property.