nik rik

static QuestionTypeCheckBox _obj;
        public static QuestionTypeCheckBox Instance
        {
            get
            {
                if (_obj == null)
                {
                    _obj = new QuestionTypeCheckBox();
                }
                return _obj;
            }
        }

        public FlowLayoutPanel  pnlView
        {
            get { return pnl_main; } // имя элемента 
            set { pnl_main = value; }
        }

        private void DeleteQuestionButton_Click(object sender, EventArgs e)
        {
            ...
             FlowLayoutPanel.Instance.pnlView.Controls.Clear(); // Удаление контролов
        }