private void buttonAccept_Click(object sender, System.EventArgs e) { //Button "Accept" clicked, carry out the promotion if (comboBoxFigures.SelectedItem == null) { MessageBox.Show(this, "You must select a figure", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { promotionRealized = true; //Delete the pawn Board.getInstance().killPiece(pawn.getPosition(), true); //Create the new figure string fig = comboBoxFigures.SelectedItem.ToString(); Position pos = pawn.getPosition(); Color color = pawn.getColor(); Piece piece = null; if (fig == "Bishop") { piece = new Bishop(pos, color); } else if (fig == "Knight") { piece = new Knight(pos, color); } else if (fig == "Queen") { piece = new Queen(pos, color); } else if (fig == "Rook") { piece = new Rook(pos, color); } if (color == Color.White) { Board.getInstance().getWhitePieces().insert(piece); } else { Board.getInstance().getBlackPieces().insert(piece); } Board.getInstance().deletePiece(pawn); Board.getInstance().drawPiece(piece); this.Close(); } }