private void button7_Click(object sender, EventArgs e)
        {
            var form = new ChooseDubbedPieceWhite();

            form.Location = this.Location;
            form.ShowDialog();
            // code will freeze here until that form is closed

            string chosen = form.chosen;
        }
        private string Promote(int i)
        {
            var    form1 = new ChooseDubbedPieceWhite();
            var    form2 = new ChooseDubbedPieceBlack();
            string chosen;

            if (i == 0)
            {
                form1.Location = this.Location;
                form1.ShowDialog();
                chosen = form1.chosen;
            }

            else
            {
                form2.Location = this.Location;
                form2.ShowDialog();
                chosen = form2.chosen;
            }
            // code will freeze here until that form is closed

            return(chosen);
        }