Preventing a dialog from closing in the button's click event handler

Question

I have a dialog that I show with .ShowDialog(). It has an OK button and a Cancel button; the OK button also has an event handler.

I want to

Answer 1

Use this code:

private void btnOk_Click(object sender, EventArgs e) {
  if (ValidateControls())
    this.DialogResult = DialogResult.OK;
}

The problem of it is that the user has to clic two times the buttons for closing the forms;